Based on the ranking data of the best universities in China from 2016 to 2020, this paper analyzes the influence of “double first-class” policy on the source quality of undergraduates by using the single group time series experiment method in the interruptive time series quasi experiment method. It is found that there are great differences in the quality of students in “double first-class” universities, but the distribution is relatively stable. The “double first-class” policy has a certain impact on the quality of undergraduate students. 38 of Project 985 universities and 67 of Project 211 universities have further consolidated the advantage of high quality students. In addition, 3 of Project 211 universities have entered the list of first-class universities and 19 of non-Project 211 universities have entered the list of first-class disciplines and the quality of their students has improved to a certain extent. However, the quality of students in those colleges and universities with good quality but not in the list of “double first-class” construction shows a downward trend. This results from the continuity of government resource input, the orientation of social talent demand and the stability of the university’s own development.