In recent years, many universities have started implementing large-class enrollment in an effort to reduce the blindness of major selection and strive for excellent students. This entails grouping students in major categories who are majoring in the same or similar subject categories, the same department, or majors from different departments together. However, there are still some issues with large-class enrollment and major diversion that merit further discussion. The paper compares and analyzes the large-class enrollment and major diversion schemes of several typical universities, discussing the advantages and disadvantages of large-class enrollment and the major diversion model. Further, taking the civil engineering major at a certain university as an example, it analyzes the trends in educational environment and student performance before and after major diversion under the large-class enrollment background. The paper suggests that by developing more detailed admission plans, establishing more flexible major selection systems, lowering the difficulty of changing majors after admission, and creating open and transparent selection systems, the existing large-class enrollment and the major diversion schemes can be further optimized.