Provided are a method and a system for intersection space-time optimization facing tidal traffic. The method comprises: acquiring structure data and traffic operation data of an intersection; establishing a lane planning model, the lane planning model using each number of function lanes of an intersection entrance lane as variables, using equalization of each flow direction of the intersection asan objective, and using basic logic relations of the variables as constraint conditions; solving the lane planning model, to obtain a lane planning scheme; using a Webster timing method to solve, to obtain a signal timing plan. Through optimally configuring intersection space-time resources, including lane function planning and signal timing, the method and the system can reduce intersection delay, improve intersection service level, and reduce influence of tidal traffic on the intersection.