Abstract: For the purpose of preventing propylene explosion risk in production and use, propylene explosion limit was tested by 12L spherical exlosion device to study the relationship between explosion limits and various initial temperature（20~180℃）or pressure（0.1~0.9MPa）in air. The study found that with the initial temperature and pressure rising,the upper explosion limit obviously elevate,but the low explosion limit decrease slightly,the explosion limit expand. At an initial temperature of 180℃, as the pressure increases the increase of the upper explosion limit of propylene is significantly higher than the linear increase, the content of carbon powder in the explosion products increased significantly, and the lower explosion limit of propylene changed from linear to slide-like curve. The coupling effect of initial temperature and initial pressure is obviously higher than that of single factor, and the influence on the upper explosion limit is obviously higher than that of the lower explosion limit. In the range of test temperature and pressure, the coupling effect is as follows : the upper explosion limit increases by 108 %, and the lower explosion limit decreases by 18.05 %. The single factor effect of initial temperature : the upper explosion limit increased by 3.8 %, and the lower explosion limit decreased by 3.41 %.The single factor effect of initial pressure : the upper explosion limit increased by 51.3 %, and the lower explosion limit decreased by 2.44 %. In this paper, the influence surface and fitting formula of initial temperature and initial pressure on the explosion limits of propylene-air mixtures are provided.