Dynamic analysis, finite element analysis and fatigue life analysis of transmission gear of Self-Propelled Gun is achieved in this paper according to the theory of multi-body dynamics, finite element and cumulative fatigue damage, and the well-known software Pro/E, ADAMS, PATRAN and FE-Fatigue are integrated in the research. The virtual prototyping model of self-propelled gun’s transmission box is built by ADAMS software. The dynamic load spectrum of transmission gear is achieved by virtual driving of Self-Propelled Gun. The finite element model of the gear is built by using PATRAN software, after defining reasonable boundary conditions, material and element properties, according to the load and the fatigue failure criterion of the gear, the stress-strain state of gear on load is studied. The dynamic load spectrum and the stress-strain state of the gear are considered as basic input data, the fatigue life of the gear is calculated by using FE-fatigue software. The road haul of gear without fault is predicted when the self-propelled gun drives on the second-class load surface at low speed. This method offers a new idea to the fatigue life prediction. It can predict fatigue life without experiments, and save cost and time. It has the great significance to the optimization design of the self-propelled gun.