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Gas migration in a goaf is the cause of upper corner gas over limit which greatly influences coal mining safety. To explore gas migration law, this paper provides a Lattice Boltzmann (LB) simulation of gas migration in a heterogeneous goaf of a fully mechanized coal caving mining face. The goaf of a fully mechanized coal caving mining face is an area which fills with heterogeneous porous media and gas migration in it is complicated seepage movement which contains laminar, transitional and turbulent flow. Under the amended Brinkman-Forchheimer-Darcy law, this paper provides a control system which reflects the characters of gas migration law in a heterogeneous goaf of a fully mechanized coal caving mining face. Multi-components LBM is used to solve the complicated control system. Two Lattice Boltzmann Equations (LBEs) are constructed to simulate the atmosphere and gas seepage velocity field respectively. By the evolution of these two LB models, simulation results are gained. The simulation can produce many data such as speed, pressure and concentration in every time and space, thus we can get gas migration law directly. A case study showed: This method can combine time, space and system action together. It can simulate and analyze acutely the situation of gas migration in direct condition and provide an alterable method to reveal and control gas migration in an underground coal mine.