A conflict resolution method based on the cooperative game is proposed to make up for the defect of current methods in realtime multi-aircraft flight conflict resolution. Firstly, a cooperative game conflict resolution model is constructed, and the maximum coalition welfare solution is introduced to balance the benefits of all parties, which is then tested. Secondly, the evaluating indicators of conflict resolution effectiveness are studied, in the meantime, the payoff function and the coalition welfare function are put forward. Finally, the particle swarm optimization algorithm is adopted to minimize the calculation time in the solution. In the simulations of three aircraft conflict and six-aircraft conflict, this method can eliminate the strategies that violate the safety separation standard, find the equilibrium point that maximizes the coalition welfare function value, and obtain the optimal strategy of multi-aircraft conflict resolution based on preference.