Abstract: Two-stage light gas gun is one of the most widely used equipment in hypervelocity projectile launching technology, which plays an important role in a various of engineering fields such as hypersonic aerodynamics and material mechanical in high velocity impact. A two-stage light gas gun driven by gaseous detonation was designed and constructed at Institute of Mechanics, Chinese Academy of Sciences, which eliminated the disadvantages like deficient driving capability of high-pressure gas and low maintainability of gunpower. A one-quasi-dimensional numerical method was used to investigate the interior ballistic process and launching performance of detonation driving mode and pressure gas mode, the effect that the change of ignition tube position has on light gas gun and the effect of various parameters on launching performance. The result showed that the launching performance of detonation driving was superior to that of high-pressure gas driving. The contrast of forward and backward detonation driving mode showed that the change of detonation driving mode had slight influence on launching performance, but the strength design of the whole equipment had to take into consideration the driving mode. The research of various loading parameters showed the increase of detonation tube filling pressure enhanced the launching performance, beside, piston mass had complex effect on launching velocity. But the design index of light gas gun and the material performance of piston and projectile restrict the adjusting range of loading parameters. Due to the limitation, the parameters should adjust together in order to optimize the launching performance during the practical process.