The quality of undergraduate enrollment is the starting point of higher education quality. During the transition from mass to universal higher education, understanding the quality of undergraduate enrollment is of great significance for improving the teaching quality of colleges and universities and building first-class undergraduate education. Based on the data of NCSS, this study evaluates the characteristics of undergraduate enrollment quality, and further explores the impact of higher education expansion on undergraduate enrollment. The results show that, firstly, although the students’ achievements decline, their abilities increase; the profession and university’s suitability show an upward trend; fairness is generally stable but lacks diversity. Secondly, the applied universities have assumed greater responsibility in the expansion, facing multiple challenges, such as a large decline in the students’ scores, insufficient profession and university’s suitability, and insufficient diversity of students. And the research universities should pay more attention to the fairness. The research suggests that the research on quality of undergraduate enrollment should be shifted from the comparative purpose to the cognitive purpose, so as to help colleges and universities improve education and teaching based on the quality of student resources and realize the value-added development of college students. And it is suggested to provide certain policy and resource support for the development of applied universities, so as to cover a wider range of undergraduate students and build a more extensive sense of first-class undergraduate education.