The valve of a certain type of APU often didn’t close with abnormal vibration noise when it testing under the specified pressure.This paper ensured the key cause of fault and opening range change due to valve structural parameter change by structural principle study, theory character analysis of circular frequency, Fluent simulation analysis and test inspection on-site, the result showed which can change close pressure and opening rate range of the valve by means of control the depth of valve shell, by which can gain the better noise and vibration reduction effect, it is significant and acting to remove this kind...