Based on the each influent factor of Fick diffusion law,through the derivation,the expression formulation of diffusion coefficient is obtained.According to the analysis of formulation,the main influence factor for coal mine dust diffusion coefficient is obtained,and the impact law of influence factor for dust diffusion coefficient and dust concentration is studied.The research results show as follows:the dust diffusion coefficient is influenced by temperature and dust size,and the temperature is relative smaller.The smaller the dust size,the bigger dust diffusion coefficient becomes,the faster the dust diffuses,and the tendency is more obvious for the dust size less than 1μm.The research has referential value for dust preventive treatment of coal mine.