To improve the respirable dust diffusion model in the fully mechanized working face, based on the theoretical model of aerosol mechanics and fluid dynamics and combined with the actual environment, the respirable dust diffusion model was established by coupling two dust sources of the frame shift and cutting coal. In this process, the treatment of two-time respirable dust was mirror image method. In order to solve the turbulent diffusion coefficient and longitudinal dispersion coefficient of the mathematical model, the experimental site was set up by the ratio of 3:1. Then some experiments were carried out and gradient descent method was used for parameter estimation. Turbulence coefficient value was applied to calculate the respirable dust mass concentration. Then comparing theoretical value with experimental value, results showed that: in the 258 sampling points, the average absolute error rate is 29.66%. It indicated the reliability of the theoretical model, which can be used to predict the dust mass concentration in the actual underground space