Generally speaking, pre-defense is to defend in the paper group, show your graduation thesis and PPT to the tutor and the students in the group to judge whether there are any loopholes, and then the tutor gives relevant suggestions and initially puts forward some defense questions to prepare for the formal defense. Pre-defense is relatively simple. My tutor will not ask particularly deep questions, but the formal defense will be more strict and standardized. The teacher will check whether it meets the graduation standards and ask difficult questions. Hope to adopt.