In order to investigate the ignition mechanism of HTPB propellants under high pressure waterjet, HTPB propellant of different formulas was used under high-pressure water jet impact research, conducted SEM analysis and infrared spectra analysis to the propellant before and after impact. The results showed that the surface morphology and composition of HTPB propellant was changed during the process of the impact of high-pressure waterjet, and propellant was chemical changed, and the composition of ammonium perchlorate and ferrocene affected the chemical change significantly.