Through the vibration transfer path analysis inside axial piston pump, the shell is gotten as the final receptor of vibration. The shell modal analysis was carried out by aimed at the shell under normal working condition. Shell supports were simplified as elastic ones, and the effect law of support stiffness to natural frequency of the axial piston pump was investigated. With the response spectrum analysis method, the maximum displacement and maximum stress of shell under the transient load of the shell were analyzed and got its change rule with support stiffness. The results show that the higher support stiffness, the higher natural frequency of the pump is, and the increase of support stiffness will reduce stress of pump, but when stiffness is close to fixed stiffness, if to increase stiffness continuously, the effect of vibration reduction is no longer obvious.