Problems existing in information comprehensive utilization and management in power plants in China are analyzed. Architecture of Web Services and operation pattern of Web Services are expounded. Comprehensive information integration of power plants in wide area net (WAN) based on Web Services is expounded in detail in framework and features. Comprehensive information integration for power plants in WAN is expounded with optimum selection of equipments in power plants as a case. Service providers consist of modules in 4 levels in optimum selection of equipments, which are data acquisition module, optimization caller module, statistics module, optimization implementation module and system management module. Local node acquires massive information and data dealing with equipments with optimization caller module provided by other nodes in WAN. Optimum selection of equipments is implemented with other nodes providing statistics services and optimization implementation services to provide support for managers' decision-making of local node power plant. Operational result of the designed information platform shows that data exchange between different node power plants and inter-operability between heterogeneous subsystems are implemented successfully and mutual supplementary of advantages and information sharing between different power plants are improved greatly.