Thermal analysis curves of two proportions of sulphur-free black powders were measured by differential scanning calorimetry (DSC) at heating rates of 2,5,10,20 ℃·min^-1. The data and thermal behaviors were contracted between sulphur-free black powder and ordinary black powder. On the base of experiment data, activation energy and pre-exponential factor of black powder were calculated according to Kissinger′s equation,Ozawa′s equation and Satava-Sesták′s equation. Results indicate that the initial exothermic temperature，heat release and mechanical sensitivity of sulphur-free black powder are lower than these of ordinary one when active energy is higher.