This is not an explicit rule, but just a default requirement of the school that accepts the graduate school students, if the students even their own defense is not good, proving that in some aspects of the knowledge or ability is insufficient, the school will reconsider whether to accept the graduate school students. Therefore, it is better for students to work hard on their graduation design and prepare for their defense. Of course, the teachers of this school know that this student is a graduate school students, will also relax the defense of the graduation design to give high marks.