Bad firing precision, huge consumption of projectiles in test and launch unsafety are the three difficult technology problems constraining the development of modern rockets and gun weapons. Firing precision and the launch safety of weapon system depend on dynamics style of weapon system. As a engineering subject of multidisciplinary approach studying the motion styles of weapon system and the force acting on it during launch process, launch dynamics has been a new technological breakthrough in improving firing precision and launch safety of rockets and gun weapon system in the world, provided new theory and technology for design and test of firing precision and launch safety. In this paper, theory and technology of launch dynamics of multibody system and its applications in design and test of firing precision and safety for rockets and gun weapons are studied.