Abstract: Due to the blindness of the current “trial and error method” used in determining the microscopic parameters in the PFC^2D， a microscopic parameters determination method was put forward based on physical experiments. The physical and geometrical parameters of the simulation model were obtained by simulating the basic characteristics of real samples， and the contact constitutive parameters between particles were back calculated base on the physical test responses. Taking the mylonite of -450 level footwall in Jiaojia gold mine as an example， the micro parameters of the corresponding numerical model were determined， and uniaxial and biaxial simulation were carried out based on the uniaxial compressive physical test. The simulation results and physical responses have good consistency， which verifies the reliability and applicability of the proposed method. The PFC^2D microcosmic parameters determination method can ensure simulation accuracy， reduce the early modeling workload and offer references for similar researches.

Key words: PFC^2D, numerical simulation, microscopic parameter determination, trial and error method, back calculation