The kinetics of leaching arsenic from Ni-Mo ore roasting dust was investigated. The effects including leaching temperature, particle size of the smelter dust, stirring speed, the coefficientβ(the molar ratio of sodium chlorate to arsenic in the smelter dust) and the initial H+ concentration on leaching arsenic were studied. The results indicate that the leaching of arsenic increases sharply with the decrease of particle size. The orders of reaction with respect to H+ concentration and particle size are determinted to be 1.136 and-1.806, respectively.The leaching of arsenic reaches 99% under experimental conditions, the apparent activation energy is determined to be 11.157 kJ/mol, which is consistent with the values of activation energy for diffusion model. The kinetics equation of leaching arsenic from the roasting dust could be expressed by a semi-empirical equation as 1-2/3η-(1-η)2/3=k0(c[H+])1.136r0-1.806exp[(-11157/RT)t].