Graduation thesis is an important part of undergraduate education talent training plan in colleges and universities, and it is also the last and most important practical teaching link in undergraduate teaching process. It plays an important role in cultivating and training students' ability to solve practical problems by comprehensively applying basic theories, basic knowledge and basic skills, achieving the training objectives and enabling students to adapt to their jobs better and faster after graduation. Therefore, many colleges and universities attach great importance to this work and have carried out some exploration and research. In this special teaching practice, through continuous thinking and practice, the teaching method of guiding undergraduate graduation thesis has been reformed. This paper is some practices and experiences in this field in recent years. The topic selection of graduation thesis is an important teaching link for undergraduates to obtain bachelor's degree, which enables students to independently complete the design, operation, data processing and result analysis of an experiment under the guidance of tutors, further master the basic theories they have learned, cultivate students' ability to analyze and solve problems, and exercise their ability to work independently. At the same time, according to the characteristics of undergraduates, the following aspects should be considered when choosing a topic for graduation thesis.

The training goal of this major is to cultivate students' all-round development in morality, intelligence, physique, aesthetics and labor, so that they can have the theoretical basis of life science and systematic biotechnology theory, basic knowledge and skills, engage in scientific research or teaching in scientific research institutions and colleges, and work in enterprises, institutions and administrative departments in industries such as medicine, food, agriculture, forestry, animal husbandry and fishery, environmental protection, gardening and marine biological engineering. When choosing a topic for students' graduation thesis, we should first consider the consistency with the training objectives of this major. The existing conditions of the school have defined the professional training objectives. When selecting a topic, we should combine the existing conditions of the school, make full use of the existing conditions of the school according to the conditions of laboratory instruments and equipment, and carry out experimental research with higher level and updated content. The tutor's topic selection and funding should be combined with the tutor's research topic or project, especially in the case of limited funding for undergraduate graduation thesis experiment, it is difficult for the tutor to complete the graduation thesis experiment without scientific research topic. Instructors of students' level and ability should also consider the actual situation of students when choosing topics, and draw up difficult (difficult, medium and easy) topics suitable for students of different levels. On the one hand, we should let students with good learning foundation make high-quality papers, on the other hand, we should take care of poor students to complete a complete experiment and reach the level required by bachelor's thesis.

The design and implementation of graduation thesis experiment is the key to cultivate students' practical ability, and the instructor should devote enough energy to the whole process of tracking and managing the experiment. Through two-way selection, students choose their favorite subjects and teachers and enter the laboratory to carry out experimental research. Instructors should seriously guide, arrange and teach students the basic ideas and methods of experimental research. In the process of guiding students' graduation thesis, regular meetings are held, students report the progress of the experiment, put forward the problems encountered in the experiment, and discuss with each other. Finally, the teacher makes a summary and answers questions to guide and solve students' problems in experimental research in time. At the same time, students are arranged on duty every week, so that self-management and everyone have the opportunity to participate in management, and students' ability to deal with people, manage things and coordinate interpersonal relationships is exercised. In students' specific experiments, teachers should grasp the experimental scheme, carry out the experiment and summarize the experiment. Teachers guide students to design experimental schemes. After reading a large number of documents, it is an important link to cultivate students' innovative ability to independently design experimental schemes under the guidance of teachers. Generally, under the guidance of the teacher, the students write the draft of the experimental scheme, and instruct the teacher to propose amendments, and then the students modify it and instruct the teacher to examine and approve it.

Through constant revision and thinking, students can gradually understand what their experiments are about, why they should do these experiments and how to do them themselves. It is the most important stage of cultivating students' practical ability and self-management comprehensive training to complete the experiment independently and guide teachers to check the implementation process of the experiment at any time and regularly. At this stage, we should avoid two extreme phenomena: one is that teachers let go, students decide everything, and students can't get formal professional training; The other is that teachers can't let go and take students to do everything. Students have no chance to think and practice independently, which is not conducive to the cultivation of students' ability. Therefore, when cultivating students' ability, we should pay attention to some small things, such as washing dishes and dispensing medicines. At the same time, pay attention to cultivate students' rigorous scientific attitude and record the experimental results truly. Summarize the stages and constantly improve the experiments of experimental students. Make a stage summary every 2-3 weeks, find problems in time, and constantly improve the experiment. Do things that cannot be pushed, counted or checked, and "settle accounts after the autumn", because if problems are made in this way, there is no chance and possibility to remedy them.