In order to verify the rationality of the design of certain type vehicle-borne rapid-fire mortar, the Abaqus finite element software was used to analyze the finite element mode of the vehicle-mounted rapid-fire mortar. Using the method of equivalent mass, a 3-D model was built in Solidworks. The finite element model analysis of the assembly structure of the upper frame, the automaton, the high and low machine, and the first 20 order natural frequencies and vibration modes were got. The research results show that this design is reasonable and can avoid the firing frequency of mortars. It can provide reference for the further structural optimization of the upper frame and the firing test of the weapon test base.