The extracting bullet force is one of the main performance of bullet, for acquiring extracting bullet force data, on the basis of elasticity, three models are established at the junction of the warhead and cartridge. According to the Lame’s formula, the radial and circumferential stresses of the three models are obtained. Combined with the boundary conditions of the interface of the three models and the generalized Hooke’s law, the relationship of the pre-stress and the magnitude of interference are established. The extracting bullet force is obtained by the relationship of the pre-stress and the frictional force at last. The experimental value shows that the error of the extracting bullet force calculated by the formula is 8.9%, less than the engineering allowable error 15%, which proves that the formula can accurately calculate the extracting bullet force.