Armature is the core component of the six pole track electromagnetic launcher. Ablation and transition phenomenon of the armature seriously affect the emission performance during the launching process. These phenomena have an direct relationship with the structure size of the armature. Using the finite element simulation software ANSYS Workbench to simulate the assembly process of the armature and the track,and the change of equivalent pressure of the contact surface during the assembly process is obtained. Two non-uniform coefficients are proposed to characterize the non-uniform pressure distribution of the transverse and portrait. The variation law of two non-uniform coefficients with armature structure parameters is obtained. The two non-uniform coefficients increase with the increase of armature head thickness and decrease with the increase of tail length. With the increase of the tail thickness,the transverse non-uniform coefficient increases and the longitudinal non-uniform coefficient decreases. With the radius of the circle increasing,the transverse non-uniform coefficient increases,the longitudinal non-uniform coefficient is almost unchanged.