Abstract: In order to analyze the effect and mechanism of three flame retardant powders，namely，Ammonium dihydrogen phosphate (ABC)，Melamine Pyrophosphate (MPP)，and Melamine Cyanurate (MCA)，on suppressing the explosion intensity of zirconium dust clouds，A 20-L near-spherical explosion test system and a thermogravime-tric and differential thermal analyzer were used to carry out experiments． The results show that all three flame retar-dant powders can effectively inhibit the explosion intensity of zirconium dust clouds． ABC powder has a significant advantage in inhibiting the explosion of zirconium dust clouds，and ABC powder of 200g/m 3 can completely inhibit the most violent explosion of zirconium dust clouds． When the mixture of zirconium powder and these three kinds of flame retardant powders are heated in air atmosphere，the process of variation appears to be from weight gain to weight loss then to weight gain，and from exothermic reaction to endothermic recreation then to exothermic reaction．The lower decomposition temperatures of flame retardant powder are，the better inhibiting performance of oxidation of zirconium powder is． When the mass ratio of zirconium powder to flame retardant powder is 2∶ 1，the starting temperature of the rapid oxidation reaction of zirconium powder augment from 257. 08 ℃ to 591. 45，581. 43 and 401. 30℃ with the additions of ABC，MPP，and MCA powder，respectively． ABC powder possesses the best inhi-bition effect on the explosion of zirconium dust clouds among the tested samples because of ABC powder prolonging the time of rapid oxidation reaction of zirconium powder，enhancing the starting temperature of rapid oxidation of zirconium powder，and maximizing the inhibition of the combustion process of the zirconium powder．

Key words: zirconium dust clouds, explosion, thermogravimetric and differential thermal, decomposition tem-perature, inhibition