Abstract: In order to determine the rational determination of rock pillar between two pre-driven roadways, crossing through 13.5 m throw fault is taken as engineering background. We adopt UDEC numerical simulation method to research the variation of vertical stress and plastic zone of rock pillar, and the roof and floor convergence of pre-driven roadway, the rational determination of rock pillar between two pre-driven roadways is 3 m, and its rationality is verified in the engineering practice.