NOVELTY - The method for operating a gas turbine power plant with fuel cell (15) for carbon dioxide separation from the exhaust gas stream of gas turbine (3), comprises splitting the gas turbine exhaust gas (19) before introducing into the fuel cell into a cathode mass flow (20) and a recirculation mass flow (21), introducing the cathode mass flow into cathode inlet of the fuel cell and cooling the recirculation mass flow and then recirculating into suction flow of the gas turbine. The carbon dioxide and/or oxygen concentration of the gas turbine exhaust gas is regulated.    USE - Method useful for operating a gas turbine power plant with fuel cell for carbon dioxide separation from the exhaust gas stream of the gas turbine.    ADVANTAGE - The method ensures simple, efficient and safe operation of a gas turbine power plant with less consumption of energy.    DETAILED DESCRIPTION - The method for operating a gas turbine power plant with fuel cell (15) for carbon dioxide separation from the exhaust gas stream of gas turbine (3), comprises splitting the gas turbine exhaust gas (19) before introducing into the fuel cell into a cathode mass flow (20) and a recirculation mass flow (21), introducing the cathode mass flow into cathode inlet of the fuel cell and cooling the recirculation mass flow and then recirculating into suction flow of the gas turbine. The carbon dioxide and/or oxygen concentration of the gas turbine exhaust gas is regulated through the regulation of the recirculation mass flow, which is regulated as function of an operation parameter of the gas turbine. The recirculation mass flow is regulated as function of the load of the gas turbine and/or the turbine inlet temperature and/or the position of an adjustable condenser outlay. The carbon dioxide and/or oxygen concentration of the gas turbine exhaust gas and/or the condenser suction air of the gas turbine are measured and the measured value is used as input for the regulation of the recirculation mass flow. The inlet temperature of the cathode mass flow in the cathode side of the fuel cell is regulated through the regulation of the recirculation mass flow and/or a re-cooling temperature of the recirculation mass flow. Between the gas turbine and the fuel cell, a temperature-control-waste heat boiler with regulatable waste heat power is arranged and the inlet temperature of the cathode mass flow is regulated in cathode side of the fuel cell over the regulation of the waste heat power. A part of an outlet flow from the anode is recirculated in the cathode mass flow and/or is recirculated in the condenser suction gas. The conversion of the fuel of the fuel cell is incomplete in the fuel cell and a residue of the fuel of the fuel cell is burned in a catalytic burner that is arranged in or downstream of the fuel cell. The utilized waste heat from the cathode mass flow and/or in the recirculation mass flow and/or one of the waste heat flows of the fuel cell are utilized in a waste gas boiler for steam production. Carbon monoxide contained in the cathode mass flow reacts in the fuel cell and discharges as carbon dioxide from the anode of the fuel cell. An INDEPENDENT CLAIM is included for gas turbine power plant with fuel cell for carbon dioxide separation.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of a gas turbine power plant with fuel cell.    Gas turbine (3)    Fuel cell (15)    Gas turbine exhaust gas (19)    Cathode mass flow (20)    Recirculation mass flow. (21)