Abstract: Experimental research on the effects of valveless pulse detonation engine on supply system was conducted. The pressures at different positions of pipe were measured,and also used to verify the numerical simulation models of fuel pipe and air pipe. Based on the numerical model,flow characteristics of the supply system were investigated. This showed that the influences of the same head pressure on the air and fuel supplies were different. And it caused unsteady filling when the supply system was opened because of differential pressure. The unsteady filling time was fixed and determined by the given supply system. When the working frequency of the engine became larger,the ratio of this time to one cycle time increased,that is to say,more influences of unsteady feeding were imposed on the operation characteristics of the engine. Therefore,the distribution of fuel concentration was more non-uniform and the working state of pulse detonation engine was instable.