After the university starts, you can't volunteer, and basically you can't apply for a major immediately. The application for changing majors didn't start until after freshman year. But the success rate of changing majors is very low. First of all, the school will strictly limit the number of places to transfer majors (if there is no limit, everyone can transfer, so who will go to an unpopular major? ), then you should have higher requirements for grades during your freshman year (at least within the top 25% of the major rankings). Finally, the more popular the major, the more people want to change. With a limited number of places, there is great competition.