Cross-provincial emergencies are characterized by complexity, uncertainty and suddenness, with serious consequences. In practice, signing interlocal agreements, reforming organizations, conducting joint administrative conference or negotiations are the emergency coordination mechanisms among provinces to deal with it. However, the mechanisms are criticized for being illegitimate, insufficiently motivated, ineffective and limited to the provinces. Therefore, enhancing the legitimacy and effectiveness holds significant importance. In fact, the Constitution and laws provide part of the legal basis. Some mechanisms that are only for coordination are legitimate. But in order to handle emergencies better, the governments should be authorized to recalibrate the original powers according to the Emergency Response Law. The effectiveness of the mechanisms can be improved through four ways. As for interlocal agreements, the legitimacy and operability should be further improved. In addition, it is necessary to reform the emergency cooperative organization and its internal structures. Equally important is to improve the construction of information platform for accessing normalized, warning and disposal information. Finally, in order to stimulate coordination dynamics, it is necessary to increase the benefits of emergency coordination, strengthen the central government’s pressure conduction and consolidate the basis of coordination among provinces.