Abstract: This paper focuses on the study of launch dynamics for self-propelled artillery. In order to exactly compute the motion of projectile in gun tube and the initial disturbance, the theory of two-phase flow interior ballistic is applied to the study on launch dynamics. The equations group of launch dynamics for self-propelled artillery is formed, including the body dynamics equation of gun system, the dynamics equations of projectile moving in gun tube and the equations of the two-phase flow interior ballistic. For a self-propelled artillery the computational program is achieved, by which the simulation of launch process is realized. The interior ballistic, motion of projectile in gun tube, dynamic response of the artillery and initial disturbance of projectile are exactly simulated. Some computational results are in good agreement with test results. The simulation results under the classical and two-phase flow interior ballistic models respectively show that the computational accuracy will be improved when the two-phase flow model is used to study launch dynamics. This work provides a necessary base for researching firing dispersion of self-propelled artillery.