In order to solve the problem that the post-cover can’t open successfully in shock wave opening which without the fluid guiding structure in the torpedo launch case, we come up with two schemes of fluid guiding structure, simulate and analyze the flow field change of the two schemes under two locations through the software FLUENT. The result of the simulation indicates that, both of the two schemes under nearer location can reduce the top-pressure of the post-cover effectively, and make the distribution more homogeneous; compared to the nearer location, the fluid guiding result of the two schemes under farther location is worse, its top-pressure is higher, and the distribution is less homogeneous.