The science and engineering theory courses in universities account for a large proportion and are of great importance. Many basic courses in science and engineering are purely theoretical， boring， difficult for students to learn， and difficult for teachers to teach. The foundation course of science and engineering is very logical. Each course involves a large number of concepts， definitions and formulas. No matter whether it is judged or reasoned， it must follow the corresponding principles and require high abstract thinking. Moreover， the science and engineering curriculum is systematic and highly correlated， often with the basic knowledge in front and the application of basic knowledge. If the learning of the previous part is not solid， it will be difficult to follow up later. Under such circumstances， the theoretical science and engineering curriculum requires students to maintain a high concentration of attention in the classroom. The lack of a link will have a chain reaction to the later learning. In such a classroom， if the teacher blindly adopts the past teaching mode of “teacher speaking， student listening”， it is easy to cause students to shift their attention in the boring and difficult learning. Disjointed， which in turn caused difficulties in the application of relevant knowledge， and even caused students to give up the learning of the remaining courses. Therefore， ensuring the mastery of each key point of knowledge is an important means and necessary link to ensure the effective implementation of the curriculum and the efficient absorption of students.
　　What kind of method is used to collect feedback on the key points of knowledge is a problem that teachers need to seriously consider in actual operation. The traditional classroom test method involves the process of distributing， grading， and collecting. It takes a long time to collect and process the feedback. It is often impossible to know whether students have grasped the knowledge points. In the process of Knowledge Point Teaching > Classroom Test > Test Explanation in the Next Lesson， feedback and processing are out of touch， teachers cannot grasp the mastery of the key points in time， and cannot accurately judge the course and adjust the rhythm of the course.
　　Classroom questioning is also a commonly used method of on-site inspection， but it is often limited by time constraints. It can only ask one or two individual students， and it also makes the teacher's acceptance of the students incomplete， and it is easy to make mistakes. Moreover， frequent questions often increase the mental burden of students， so that students cannot pay full attention， and students who have difficulty understanding can be frustrated after answering mistakes in the classroom or in the blackboard. 　　New technologies such as the Internet provide a better solution for the timely collection and processing of student feedback. For example， the “Rain Classroom” developed by Tsinghua University is an excellent classroom teaching assistant program. I use this method to quickly collect and process a number of key knowledge points in the university's "Engineering Thermodynamics" course， and judge the trend and progress of the follow-up courses on the spot， and obtain obvious results. The process is described as follows： Teachers can use the ppt software to write questions for multiple knowledge points before class， which can be judgment questions， multiple choice questions and multiple choice questions. The test questions are scheduled to be released to the rain classroom platform based on WeChat at the appropriate time before class. After the class starts， when a key knowledge point is taught， the teacher can ask the students to answer questions about a certain concept point in the rain classroom platform of their mobile phones. After the students answer， the teacher can always grasp the correct rate of the student's answer， when correct. When the rate is above 80%， it is considered that the mastery of this key point has basically reached the requirements， and the next stage of learning can be carried out. Conversely， when the correct rate is less than 70%， the knowledge points that the other party needs to teach from another angle are needed. Carry out further elaboration and consider the reasons for the students' lack of mastery. From the time the student answers to the collection of results， the entire process takes only 2 or 3 minutes.