Abstract: In the simulation of metal powder impact compaction, the simulation model is not accurate because of the particle number difference between the model and actuality. Therefore, the relative mass was introduced as the die mass ratio between the simulation and experiment, and the influences of initial pressing velocity and particle array in transverse and longitudinal direction on the relative mass were study in this paper. The ABAQUS software was used to establish the compaction model at different initial velocity. The prediction formula was fitted by 1stOpt software. Finally, the simulation model was used to verify the prediction formula, draw the relationship between the relative mass and relative density, and obtain the relationship between the initial velocity and particle array in transverse and longitudinal direction. In the result, the final formula is obtained by using ABAQUS simulation data. When the die velocity is 20 m·s^-1, the relative mass in H₅Z₆ particle model (5 particles in transverse direction and 6 particles in longitudinal direction) is 1.03, which is closer to the actual pressing than that of the nine-particles model.