The invention discloses a biomass gasification back-heating circulation power generation system. The biomass gasification back-heating circulation power generation system comprises a combustion-supporting air conveying pipe, a heat exchanger, a tubular preheater, a tee pipe, a gasification agent conveying pipe, a biomass gasification furnace, an adsorption-type tar processing tower, a power generation internal combustion engine, an oxidant conveying pipe, a biomass gas conveying pipe and a tail gas discharging pipe. By adopting the biomass gasification back-heating circulation power generation system, the energy utilization efficiency is high, active carbon formed by gasifying biomass can be used as an absorption agent of the adsorption-type tar processing tower to split tar in biomass gas, and the processed gas can be used by the power generation internal combustion engine.