The quasi one-dimension compressible flowfield coupled to the three-dimension propellant grain regression solved by the level-set method was used to simulate the transient internal ballistics of solid rocket motor. One-dimension flowfield instead of three-dimension can save computational cost on the premise of calculation accuracy because the radial and azimuthal variations parameters have little contribution to the internal flowfield. The grain regression in real-time could provide accurate geometrical information for simulation. A combination of flowfluid solver and grain regression can reappear in a relatively real internal ballistic flowfield, so it is good for further studying the instability of solid rocket motor. For level-set equations, the total variation-diminishing second-order Runge-Kutta method for temporal derivatives and a fifth-order weighted-essentially-non-oscillatory scheme for spatial derivatives were used. The total variation-diminishing MacCormack method was used to discrete the Euler equations in flowfield solver. Two modules of this code were tested in this study:one is the burning rate module and the other is the nozzle erosion module. Results show that the burning rate influenced the solid rocket motor efficiency, and the velocity profile in the chamber was affected by the nozzle shape, and the nozzle erosion could influence the head-end pressure spike.