In order to study the mechanism of the inner cover on the coating, the tracer method was used to find the material boundary of the jet and the body. Two kinds of metal materials were designed on the two sides of the dividing line, and the AUTODYN simulation was used to form the jet. The jet forming and the concrete penetration were studied by contrasting the single layer and double-layer liner, the center perforation and the non-perforated double-layer liner. It is found that the double-layer liner obviously improves the speed of the jet head, deepening the penetration depth, but the diameter is small. In a certain range, double-layer liner opening can improve the jet velocity, which makes penetration depth and aperture optimized. Therefore, the head speed and penetration depth can be improved when the outer cover is smaller than the internal acoustic impedance and the liner is opened.