This paper reports development of a new trigger system for a high speed gas gun and experimental results on muzzle speed ofa spherical ceramic projectile launched by a gas gun equipped with the new trigger system. A new trigger system was designed carefully using numerical simulation of interaction between a trigger system and a projectile, and deformation of the trigger system. Launching pressure levels are precisely adjustable by changing trigger system parameters. Calculated launching pressure agreed well with experimental result. It was concluded that a gas gun equipped with this new trigger system can work out more powerful as compared with a commercial air rifle