The embodiment of the invention provides a power management system. The system comprises a collection module, a materialized window, a first query unit and an execution module, wherein the collection module is used for collecting and sending data stream; the materialized window is used for saving the status information of an electrical appliance used by a user and modifying the real-time information of the used electrical appliance according to a used electrical appliance operating instruction of the query unit; the first query unit is used for receiving the data stream of load information and comparing the current load and a reference load, if the current load is smaller than the reference load, a first output steam is generated for instructing the startup of the used electrical appliance; if the current load is larger than the reference load, a second output stream is generated for instructing the close of the used electrical appliance; and the execution module is used for receiving an output steam and executing the corresponding power management operation according to the instruction of the output steam.