Introducing new courses is an important part of classroom teaching. A good beginning is half the battle. At the beginning of a class, it is very important to quickly concentrate students' attention, bring students' thinking into specific learning situations, and stimulate students' strong interest in learning and thirst for knowledge. Therefore, teachers should seize children's curiosity, skillfully introduce new lessons and stimulate students' thirst for knowledge. The application of multimedia in teaching can effectively open the floodgates of students' thinking, stimulate association, stimulate exploration, and constantly stimulate students' excitement, thus stimulating their interest in learning and laying the foundation for the success of a class. For example, when teaching the understanding of seconds, at the beginning of class, the teacher asked: Do you like Chinese New Year? Listen to the New Year's bell. Play the video of the countdown to the Spring Festival Gala, and then ask: "Is the time and division of 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 appropriate here? If not, what is the right unit? " Introduce new courses. Let students experience the practical meaning of "second" in familiar practical situations. Through this life-oriented situation, the life problem is abstracted into a mathematical problem. Then let the students think about where seconds are used in their lives. And dynamically demonstrate life scenes such as rocket launch, traffic light countdown, Olympic running screen timing, countdown before news broadcast. In addition to deepening the impression of seconds, it also helps students realize that mathematics is around, feel the interest and function of mathematics, and have a sense of intimacy with mathematics.