Based on online teaching method of the postgraduate professional course of building energy conservation, through the questionnaire survey, the advantages and disadvantages of online teaching are analyzed, corresponding countermeasures are taken. According to the characteristics of small-class teaching, Tencent Class is selected for course recording and playback, and combined with the QQ group sharing teaching form with better screen function and smooth operation, and STU teaching mode is set up to mobilize students’ study enthusiasm, stimulate the learning motivation and professional interests, using simulation software such as digital information transform boring theoretical knowledge into dynamic interactive learning. From the perspective of professional interests, pay attention to the cultivation of the students’ ability of autonomous learning, from the view of the sustainable development of building energy efficiency and develop the students’ scientific thinking, improve the students’ innovation consciousness.