Since the jets and detonation gaseous products are separated by sharp interfaces,the traditional smoothed particle hydrodynamics (SPH) method is difficult to avoid the computational instability at interfaces.The multi-phase SPH (MSPH) method was applied to improving the stability,which smoothes the particle density and makes pressure continuous at interfaces.Numerical examples of jet forming process were used to test capability of the MSPH method.The results show that the method remains algorithm stability for large density gradient between the jets and gaseous products and has potential application to both the explosion and the jet problems.The effect of initiation ways of the shaped charge was discussed as well.