Abstract: Investigates the ignition mechanism of HTPB propellant under high-pressure waterjet. The interaction between the high-pressure waterjet and the HTPB propellant were simulated by LS-DYNA code with Eulers method. The pressure change in the propellant at different speeds and diameter of waterjet were calculated. The criterion of shock initiation of HTPB propellant with different compositions were obtained, The critical value of shock initiation decreases with the content increase of ammonium perchlorate(AP) and ferrocene in the propellant.The numerical simulation results accord well with the theoretical analysis.