The two-stage combustion method for controlling the NOx emission from a closed cycle MHD power plant is examined. The method is that fuel rich combustion is done in a high temperature regenerative heat exchanger followed by a completion of combustion downstream of the heat exchanger. Experiments on a pebble bed regenerative heat exchanger demonstrate that reduction of the excess air ratio of combustion gas is quite effective to suppress NO formation in the heat exchanger as well as to promote NO decomposition by gas phase reactions in the heat storage bed. Two new concepts of combined cycle power plants are proposed, in which closed cycle MHD, gas and steam turbines are combined. The two-stage combustion method is shown to suppress the NOx emission level significantly, without lowering the plant efficiency of the combined cycle power plants.