A good description of the power system tie-line power transfer capability facilitates the feasibility and optimality of cross-region power exchanges. However, the existing methods only consider the base scenario while N-1 contingencies are ignored, leading to inaccurate determination of the regional tie-line power transfer capability. Consequently, this paper focused on the power system tie-line exchange capability considering N-1 contingencies. First, based on the coupling relationship between the base scenario and N-1 contingencies, this paper developed a strategy to quickly determine the power system tie-line power transfer capability by decomposition. Furthermore, the impacts of units’ different control modes on the power system tie-line exchange capability considering N-1 contingencies are analyzed, facilitating the optimal allocation of cross-region power exchanges. The accuracy and effectiveness of the proposed methods are demonstrated in a provincial utility system.