Abstract: Based on the safety and economy analysis, the tail-gas recirculation in biomass pyrolysis liquefaction plant was investigated. The pyrolysis liquefaction experiments were conducted with or without the tail-gas recycling for comparison. The tail-gas was collected and then analyzed by gas chromatography. Results indicated that the major composition of the tail-gas is the same under the two different pyrolysis conditions, while the contents are different. The influence of non-condensate gas, such as CO, CO2 and CH4, to the biomass pyrolysis was theoretically analyzed, and the yield and composition of the produced bio-oil was evaluated. It is suggested that the tail-gas recirculation in biomass pyrolysis liquefaction plant is reasonable and feasible.