Based on the self-determination theory，this paper compares the intensity difference of students’learning motivation between when they are in a traditional class and a “PAD（Presentation-Assimilation-Discussion）Class” and analyzes the mechanism of students’ learning motivation in university. The conclusions of this research are as follows：（1）Students’sense of self-efficacy，autonomous experience and sense of belonging in class have a significant influence on their internalization of external learning motivations；（2）Compared with traditional class，PAD class can more effectively improve students’ sense of self-efficacy，autonomy，and sense of belonging，thus enhancing their internalization of external motivations；（3）As a communication tool，WeChat plays an important role in promoting the external motivation of students. This research offers empirical support for innovative class teaching models like “Internet+education”，PAD class and etc.，and provides a reference for the reform of college education.