Abstract: To meet the demands of long delay time in second level for small size delay equipment, Ansys software was used to simulate the heat transfer of delay equipment and calculate the delay time. The influence of working conditions on performance of delay equipment was investigated for comparison, including different environmental temperatures and different thicknesses of insulating sleeve. The results show that the speed of heat transfer at the central point of the clapboard is faster than that at the edge of the clapboard. The delay time of the equipment with an insulating sleeve is longer than that without insulating sleeve, while the inner diameter of equipment is 2 mm and its thickness of the insulating sleeve is 1 mm, the delay composition cannot be ignited. The lower the environmental temperature is, the longer the delay time, while the environmental temperature decreases to -30 ℃ and -40 ℃, the heat transferred to the right side of the clapboard is much less, where the temperature is lower than the decomposition temperature of the composition so that the delay composition cannot be ignited.