During the sliding electrical contact between the armature and the rail of the electromagnetic rail launcher, the armature material has severe wear and failure. In order to accurately predict the force and failure process of the armature, the Zwick-HTM5020 high-speed tensile testing machine was used to carry out the mechanical performance test of the armature material under the strain rate of 0.01 s-1, 0.1 s-1, 1 s-1, 10 s-1, 100 s-1, 1000s-1. The Johnson cook material model, which can characterize the elastic-plastic effect and strain rate effect of materials, is established by using the least square parameter estimation method. This has important application value for the limit design of the armature.