The experimental and numerical study for the detonation propagation on the system consisting on the explosive and various gaps was conducted.The experimental system consists of the pellet explosives and the gap materials,PMMA pipe,and two grams Composition C4 booster1).The sample explosive is a composition A5(RDX 98.8wt%).The thickness of the explosive is 5 or 10 mm,and the radius is 20mm.The gap materials are air,PMMA,and SUS304.The thickness of gap is 5 or 10 mm.Two PVDF gauges(Dynasen PVF2-11)are set to measure arrival time of the detonation wave.Using the arrival times and a distance between two gauges,the average velocity of the detonation wave is estimated.The numerical simulations are carried out and are compared with the experimental results.