The invention discloses a garbage gasification fuel gas and steam turbine combined power generation system of a humid air turbine. The garbage gasification fuel gas and steam turbine combined power generation system comprises a garbage gasification incineration system, a boiler system and a power generation system body. The power generation system body comprises a mixer, an air compressor, a compound smoke compressor, a compound smoke combustion chamber, a turbine a, a turbine b, a steam turbine, a power generator a, a power generator b, a waste heat boiler and a fed water inputting system. An inlet of the mixer is connected with a saturated steam outlet of a steam pocket and an air outlet of the air compressor. A water outlet of the mixer is connected with a water inlet of the steam pocket. A steam outlet of the mixer is connected with an overheater and the turbine a, and the turbine a is connected with the power generator a. A waste gas exhaust port of the boiler system is sequentially connected with the smoke compressor, the compound smoke combustion chamber and the turbine b. The turbine b is connected with the power generator b. The garbage gasification fuel gas and steam turbine combined power generation system can conduct large-scale garbage continuous gasification treatment, the garbage handling capacity is higher, the heat recycling efficiency is higher, and pollutant emission can be effectively reduced.