To help air traffic controller at aerodrome better control traffic in maneuvering area, a decision making assist system based on plan conflict detection and alerting is proposed. The most important feature of the proposed system is the module of taxi conflict detection. After an aerodrome controller issues taxi instructions to different flights, the module will detect the potential taxi conflict between flights based on the planned taxi routes and therefore alter the controller. Once the proposed system is used in operation, the efficiency and the safety of the taxi instructions given by the air traffic controller at aerodrome will improve, and traffic operation at aerodrome will become smoother and more efficient.