The vibration response about the rarefaction wave gun in the action of various loading is researched. Based on the actual loads act on the barrel in the launch process, the vibration response equation which considering the elastic effect of the barrel is established with the interior ballistic equations. By Rayleigh-Ritz modal method the vibration equation is dispersed to the second-order time-variant equations. After numerical calculation the vibration response and relation between vibration response and interior ballistic property in the different parameters are attained, and then the theoretical references about the optimization of firing precision and the reasonable choice of interior ballistic parameters are also attained.