Abstract: The complex inner flow-field of secondary gas injection for solid rock et motor were numerically investigated using three-dimensional average Favre N -S equations and the k-ε turbulent models. Three-order spatial scheme an d implicit point Jacobi algorithm were used to solve these equations. The basal explore of the integrant scheme for secondary gas injection vector nozzle was do ne by dint of the numerical simulation technology. The influences of the flow-f ield of secondary gas injection and the side force by different injection parame ters were studied and investigated. The results show that the position of the in jection hole, the injection total temperature and total pressure that affected t he side force of the nozzle are coupling. Moderate position of the injection ho le, hot gas and biggish injection total pressure increases the side force and ve ctor angle of the nozzle effectively. The hot gas injection system has higher ef ficiency. The side force increases linearly with the augmentation of the seconda ry injection total pressure.