The gas engine unit can utilize various combustible gases such as mashgas, landfill gas, oil field gas, coking gas, biomass gasified gas, marsh gass, coal gasified gas, nature gas and so on to generate electricity by the generator set. Utilizing the waste heat of the unit that can make refrigerating, heating, and hot water supplying. The installed capacity of the unit shall be more than 5000 KW. It is probable to take full advantage of the unit’s excess heat to produce steam by an exhaust heat boiler to drive a turbine for power generation, thereby realizing the power generation of fuel gas & steam combined circles.