Abstract: A theoretical model describing the process of the crack combustion and propagation in solid propellant was formulated.The effect of chamber pressurization on the combustion and propagation of crack was studied by testing and computation researches on the model.The results indicate that the chamber pressurization has strong effects on the convective burning in the crack,crack initiation and fracture patterns.The higher the chamber pressurization is,the greater the velocity of the burning gas flowing into the crack,the higher the pressure in the crack,and the sooner the crack fractures.The calculated results are in good agreement with experimental data,that validates the reasonableness of the theoretical model.