As the final link of quality evaluation of postgraduates'cultivation,academic oral defense system should be strictly organized to promote the training quality. Many problems such as formality of pre-defense,high proportion of personal relations and difficulty invitation for defensive experts exist in the current academic oral defense system. Aiming at the problems,the author puts forward corresponding countermeasures for the actual improvement including establishment of defensive experts bank,double-blind evaluation system of papers ,twice arrangements of pre-defense and unified organization of defensive experts on hospital level.