In order to systematically analyze the vibration characteristics of ship seawater piping system, the finite element method is used to establish the frequency domain calculation model of pump assembly-isolator-flexible adapter-tubulation-support-piping accessory system. Taking a certain seawater piping system as the study object, its natural vibration characteristics and transmission characteristics are analyzed by the numerical simulation. The results show that the stiffness of flexible adapter is the key to the vibration transmission between the pump assembly and tubulation. When it is less than 1/10 of the stiffness of vibration source pump assembly isolator, the vibration transmitted to the tubulation attenuates greatly. Optimizing the piping accessories and support structure can make the tubulation bending vibration frequency avoid the low excitation frequency of pump assembly, which is more effective to suppress the vibration transmission of specific frequency band.