The invention discloses a combined electricity, heat and gas supply system and process formed by using rice straw as raw material. It makes Spartina the best raw material source of high-quality energy and provides the cheapest clean energy for human beings. It includes Spartina gasification gas supply, power generation, and heat supply system, which is composed of feeder, gasifier, purifier, separator, fan, safety device, internal combustion engine generator set, control mechanism, etc. The gasification reaction furnace adopts a micro-negative pressure system to automatically adjust the intake air volume, gradient combustion reaction, gasification, the increase of furnace temperature promotes the cracking of tar, and the complete reaction in the furnace increases the calorific value of gas and reduces tar; , Falling film absorption and dehumidification functions in one wet purifier, high purification efficiency, one-time no power to remove ash and tar, etc., the purifier is a fully enclosed device, there is no gas leakage point, and the oxygen content of the gas is low , eliminating potential safety hazards. The special atmospheric pressure gas boiler is used for central heating, and the special gas internal combustion engine is used for power generation.