Educational technology refers to the theory and practice of optimizing education and teaching through the design, development, utilization, management and evaluation of teaching and learning processes and related resources by using various theories and technologies. Its main research fields can be answered from five aspects: the design, development, utilization, management and evaluation of teaching and learning process and related resources. The design mainly includes: teaching system design, content information design, teaching strategy, learner characteristics analysis and so on. The development mainly includes: printing technology, audio-visual technology, computer application technology and other comprehensive technologies; Utilization mainly includes: the use of media, the promotion, implementation and institutionalization of innovative technologies, policies and regulations, etc. Management mainly includes: project management, resource management, teaching system management, information management, etc. Evaluation mainly includes problem analysis, reference standard evaluation, formative evaluation and summative evaluation.