Building cooling and heating source is a core course for the major of building environmental and energy application engineering. Through the study of this course, students can master the basic theory and design method of building cooling and heating source, and independently design the complex air conditioning system, providing important support for achieving the professional training objectives. This study analyzes the teaching characteristics of building cooling and heating source course, and the existing teaching implementation process of the original course included the contradiction between the teaching content and the course credit hours, the limitation of training objectives and teaching methods. These problems cannot meet the current demand of talent training under the background of emerging engineering development. Therefore, this study has carried out reforms, such as: re-structure of teaching content, integration of online and offline teaching and diversification of teaching evaluation. The internet-assisted blended teaching is an effective way to promote the rapid and high-quality development of education and promote the progress of education. In this paper, the teaching reform of the course of building cooling and heating source is carried out and the online and offline blended teaching mode based on the Rain Classroom is explored. This study re-structured the curriculum knowledge system, integrating the teaching chapters into five modules. Online and offline teaching methods are combined, including online release preview, offline teaching and online testing, problem extention after class, and integration of knowledge and ability training. It has reformed the traditional achievement evaluation mechanism and adopted diversified evaluation methods. Through the above three aspects of reform, the path of blended teaching of building cooling and heating source is explored, and students’ ability of independent learning is cultivated, to provide reference for strengthening discipline construction and deepening core curriculum teaching reform.