The invention relates to a power-gas combined scheduling method and system. The method includes the following steps: acquiring a prediction load, supply prices of a liquefied natural gas at each and every time, the topological data of a natural gas system network, the topological data of a power system, the operation data of a coal-fired unit which takes part in the scheduling and operation and the operation data of a gas generator set, basic data of a liquefied natural gas receiving station and the operation state of the liquefied natural gas receiving station, and the information about arrival at port of a transportation ship which belongs to the liquefied natural gas receiving station; based on the aforementioned information, constructing a power-gas combined scheduling model and constraining conditions thereof, adopting a nonlinear plan solver, solving the power-gas combined scheduling model based on the constraining conditions to obtain the result of scheduling and operation of the coal-fired unit and the gas generator set, and controlling the operation of the coal-fired unit and the gas generator set based on the result of scheduling and operation of the coal-fired unit and the gas generator set. The method considers the uniqueness of the gas source of the liquefied natural gas and also the risks in supply, and has strong practicality.