During the launching process of electromagnetic energy equipment, the contact resistance between the armature and the rails are an important index to measure the contact state of the rails and can reflect the contact state of the rails during the turning of the bore. Since it is difficult to directly measure the armature-rail contact resistance during the launch process, this paper proposes a method for calculating the armature-rail contact resistance of electromagnetic energy equipment based on discrete wavelet transformation, which is based on the measurement of the muzzle voltage and current, the use of discrete wavelet transformation to de-noise the measurement data, and then combining with the recursive solving equations of the muzzle circuit model, the size of the armature-rail contact resistance is calculated and analyzed in comparison to that of the Fourier transform results. Compare and analyze with the results solved by Fourier transform. It is found that the contact resistance of the armature-rail is large at the beginning, then decreases rapidly and has a tendency to rise, and finally increases rapidly at the moment of the muzzle discharge. The numerical calculation method proposed in this paper has important reference value for solving the armature-rail contact resistance of electromagnetic energy equipment.