Aiming at the problem of pressure parameter optimization in grouting reinforcement of broken surrounding rock of roadway, the goaf of Ludong Mine in Yunnan Province was taken as the engineering background, a numerical model of grouting diffusion of broken surrounding rock was constructed based on COMSOL Multiphysics software, and the seepage law of slurry under 1.0 MPa, 1.2 MPa and 1.4 MPa grouting pressure was systematically simulated. The results showed that in the early stage of grouting diffusion, the higher the slurry pressure, the greater the driving force of the slurry under pressure, and the faster the slurry diffusion ; when the grouting time was extended to the middle and late stages, the increase of grouting pressure on the effective diffusion distance was significantly weakened. With the increase of grouting pressure, the diffusion radius of slurry also increased. However, when 1.4 MPa was compared with 1.0 MPa, the diffusion distance only increased by 4.8 %, while the effects of 1.4 MPa and 1.2 MPa were similar. Considering the economy and engineering benefits, the optimal grouting pressure was recommended to be 1.2 MPa. The relevant research results could provide a theoretical basis for the optimization of grouting parameters of broken surrounding rock.