Abstract: Based on the principle of virtual displacement, the master-slave method formula for three-dimensional dynamic finite element problems was derived, and the master-slave analysis function of finite element was improved by optimizing the variable labeling process. Theoretical analysis shows that the improved master-slave analysis method must strictly comply with the linear correlation between degrees of freedom, and the mass, damping, stiffness and load in the dynamic equation must be accumulated according to their weights; The traditional two degrees of freedom coupling method is only a special case of the master-slave method, and the theoretical basis of both is guaranteed by the principle of virtual work. Numerical examples demonstrate that the computational accuracy of the improved master-slave analysis method is related to the grid density and stiffness of the primary and secondary domains; When the nodes of the main domain and the sub domain are not completely one-to-one corresponding, the grid density of the main domain should be greater than that of the sub domain. A main domain with sparse grid density may have significant computational errors; Reasonably selecting the calculation method of master-slave weights can improve the accuracy of numerical solutions. Research has shown that the improved master-slave analysis function is reliable and can reasonably simulate the same contact force behavior between points, lines and surfaces. It can meet the modeling requirements of complex contact nonlinearity and greatly enrich the applicability of the self-developed finite element software ZQFEM. It is of great significance in the application of contact nonlinearity and autonomous programming.