NOVELTY - A purifying system comprises burner for generating inner heat source with high temperature required by thermolysis furnace; high temperature thermolysis furnace for generating biomass thermolysis gas; high temperature air gasification furnace for generating gasified gas; and catalyzing purifying device for high temperature thermolysis gas. A high temperature air and liquefied oil gas (or natural gas) are burned in burner to generate high temperature smoke gas with temperature of 2000 degrees C.    USE - A purifying system for high temperature thermolysis catalysis and gasification of biomass.    ADVANTAGE - The purifying system solves the problem of tar pollution of biomass thermolysis gasification, and increases thermal value of biomass fuel gas by using water to remove tar, thus making it suitable for industrialization.    DETAILED DESCRIPTION - A purifying system comprises burner for generating inner heat source with high temperature required by thermolysis furnace; high temperature thermolysis furnace for generating biomass thermolysis gas; high temperature air gasification furnace for generating gasified gas; and catalyzing purifying device for high temperature thermolysis gas. A high temperature air and liquefied oil gas (or natural gas) are burned in burner to generate high temperature smoke gas with temperature of 2000 degrees C. The high temperature smoke gas acts as inner heat source with high temperature of biomass thermolysis furnace. The biomass in thermolysis furnace performs thermolysis reaction in inner heat source with high temperature to generate biomass thermolysis gas. A tar carried by biomass thermolysis gas performs intense secondary thermolysis reaction in high temperature thermolysis furnace so that the tar included in thermolysis gas is greatly reduced. Two thermolysis furnaces are alternatively used to produce thermolysis gas. An inclined grid plate (which and plane have included angle of 30-45 degrees ), acting as uniformly distributed inner heat source, is provided at bottom portion of thermolysis furnace, and has function of turning the residual carbon matching with compressed air device. The gasification furnace used by residual carbon in biomass thermolysis furnace produces biomass gasification gas, with high temperature air as gasification medium of residual carbon. The temperature of biomass gasification gas exhausted from thermolysis furnaces reaches 1200 degrees C. The high temperature thermolysis gas enters into catalysis cracker with special structure. The catalyst dolomite dust (having grain diameter of 0.2-1 mm) jetted from top portion of cracker and high temperature thermolysis gas entering from bottom portion of cracker have enough time to contact so that the cracking rate of tar is very high. The thermolysis gas, comprising little tar and exhausted from catalysis cracker, enters into high temperature air heat accumulator. The heat accumulator removes tar solidified in channel by switching direction of air channel and fuel gas channel. The thermolysis gas with tar content less than 10 mg/m3 is sent into gas storage holder.