The invention relates to a combined starting device of a gas turbine engine for guided missiles. The combined starting device comprises an electric starter (2), a starting turbine (4) and a gunpowdergas generator (6). The electric starter (2) is mounted in the gas turbine engine for the guided missiles. The starting turbine (4) is mounted at the tail of the gas turbine engine for the guided missiles. The electric starter (2) and the starting turbine (4) are connected with an engine rotor (3). The gunpowder gas generator (6) is connected with the starting turbine (4) to blow and rotate the starting turbine (4). By means of the device, the belt rotating speed of the gas turbine engine can be remarkably increased, the aerial starting success rate of the engine can be improved, the starting time of the engine can be shortened, and therefore the operational effectiveness of onboard air-to-ground guided missiles can be improved, and the work reliability of the guided missiles can be improved.