In early period of electricity market under deregulated environment， the yearly and monthly contract trade is firstly opened， then the day-ahead electricity market and real-time electricity market are opened gradually. In the northeast China regional electricity markets， only yearly and monthly contract trade is opened and this state may persist three to five years. In this context， peak load dispatching has become the problem to be urgently resolved. The basic frame of peak load dispatching is built in this paper and symplectic coordination method is also presented. Based on the response ability of generators and the network loss incremental ratio of generators， the generating units are divided into two groups: the symplectic generators lack of regulating capacity and the symplectic generators surplus of regulating capacity. The regulating models for two groups are constituted. The former will be supplemented and the latter will be released. By this means， active power can be reserved in advance during peak load for fear of the response capability lack. The proposed method considers not only improving response ability of climbing the peak load， but also decreasing network loss and avoiding congestion. Its feasibility is proved by a practical system case.