Abstract: For the purpose of preventing sulphur dust explosive risk，the autoignition temperature（AIT），self-heating properties， thermal stability，minimum ignition energy（MIE），minimum explosion concentration（MEC），explosion pressure，and explosion index of sulphur dust were tested.The risk degree of explosion was graded based on the experimental data.Results showed that with the decrease of the particle size，the autoignition temperature，minimum ignition energy，and minimum explosion concentration of sulphur dust decreased，but the explosion pressure and explosion index increased；the explosive hazard of sulphur dust with particle size under 70 μm was the most dangerous，because its autoignition temperature was 220 ℃，minimum ignition energy was 0.14 mJ，and minimum explosion concentration was 17.5 g/m3.Furthermore，the maximum explosion pressure reached 1.15 MPa and the dust explosion index peaked 39.87 MPa·m/s.The explosion risk levels of sulphur dusts with particle size above 375 μm were all St3.

Key words: sulphur, autoignition temperature, minimum ignition energy, minimum explosion concentration, explosion index