In this paper a new type of experimental device that can be used to visualize liquid injection process, whose power source is burned gas produced by combustion of solid propellant is presented. This system uses flash X-rays to study the divergence structure of high-speed liquid jet nucleus. The effects of back pressure, nozzle structure, etc. on liquid jet breakup are studied in the confined space. The results are important to adjust combustion chamber geometry and control combustion stability.