The invention discloses a biomass gas making system and a biomass gas making technology based on microwave heating. The biomass gas making system comprises a microwave gasifier, a heat exchanger, a cleaning and dedusting device and a gas accumulation device, wherein the microwave gasifier, the heat exchanger, the cleaning and dedusting device and the gas accumulation device are sequentially connected; the heat exchanger is used for carrying out heat exchange with gas generated by the microwave gasifier; air and water enter the heat exchanger from one end of the heat exchanger and can be input into the microwave gasifier through the other end of the heat exchanger after being subjected to the heat exchange with the gas generated by the microwave gasifier; a residue outlet of the cleaning and dedusting device is connected with the microwave gasifier. The biomass gas making system disclosed by the invention has the beneficial effects that a biomass gasifying conversion process can be strengthened by utilizing the combined action of heat of materials per se and microwave auxiliary heating, the temperature needed for splitting and gasifying of plant materials can be rapidly reached, the gas production rate is high, and efficient and clean energy conversion on biomass type waste resources can be realized; sensible heat and waste heat which are generated during a gas making process can be fully utilized, the heat utilization rate is high, and the energy source is saved; automatic feeding and automatic discharging can be realized by the whole gas making device, the automation degree is high, and the safety is high.