The integration method of Birkhoffian systems in event space was studied, and the parametric equations of the Birkhoffian systems in the event space were given. By choosing a Birkhoff’s variable in the event space as the function of the rest of the variables, the basic system of quasilinear partial differential equation was se tup, and the idea of field method was generalized to the integration of Birkhoff’s parametric equations in the event space. Since any Birkhoff’s variable can be chosen as the function of the remaining variables in a specific problem, so the method has flexibility. The major difficulty of this method lies in how to find the complete solution of the basic partial differential equation. Once the complete solution was found, the motion of the systems can be obtained without doing further integration. At the end of the paper, an example was given to illustrate the application of the results.