A distributed energy storage (DES) electromagnetic railgun has the advantage of higher efficiency, compared with a breech-fed railgun. A railgun with a caliber of 60 mm×80 mm is designed. In order to stabilize the current waveform, current feed-in points are set along the length of the gun, and the armature position is diagnosed and the pulse power system is triggered by real-time feedback signal to test the performance of the DES railgun. The resistance gradient is calculated by finite element analysis: the coupling field of current field and magnetic field is applied to the rectangular rail-armature model established in the 3D magnetic field of COMSOL. Based on the platform of MATLAB SIMULINK, the power circuit of capacitive energy storage pulse power supply module is established. The impedance models of rail and armature are established according to the non-linear time-varying dynamic characteristics of DES electromagnetic railgun, and the forward electromagnetic force and sliding friction force are calculated to construct the motion equation of armature. The armature-railgun module is built by signal circuit, and the two isolated networks connected through SIMULINK measurement module. The variable step-size ode23tb solver calculate the railgun current and exit velocity. A 4.16 MJ DES electromagnetic railgun is designed. The results show that with 10.8 kV pre-charging voltage of the capacitance, a 3 m long DES electromagnetic railgun can accelerate the 1 kg projectile to 1.4 km/s. Compared with the breech-fed electromagnetic railgun, the launching efficiency of the system can be increased by about 3%.