NOVELTY - Reducing flue gas emission during biochar preparation process comprises providing organic materials to prepare biochar generated flue gas and obtaining the biochar, leading the flue gas into primary leaching tower, carrying out primary washing and passing into a secondary leaching tower for secondary washing and then discharging, where washing water generated during the primary and secondary leaching is filtered via a carbon filter, passing the filtered water into the primary and the secondary washing tower and carrying out anaerobic digestion after repeated washing and filter circulation.    USE - The method is useful for reducing flue gas emission during biochar preparation process (claimed).    ADVANTAGE - The method generates available new energy resources; is highly efficient, environmental-friendly and achieves recycling economy in the charcoal preparation process.    DETAILED DESCRIPTION - Reducing flue gas emission during biochar preparation process comprises providing organic materials to prepare biochar generated flue gas and obtaining the biochar, leading the flue gas into a primary leaching tower, carrying out primary washing and passing into a secondary leaching tower for secondary washing and then discharging, where washing water generated during the primary and secondary leaching is filtered via a carbon filter, passing the filtered water into the primary and the secondary washing tower for washing flue gas and carrying out anaerobic digestion after repeated washing and filter circulation to obtain combustible gas. An INDEPENDENT CLAIM is also included for device for reducing flue gas emission during biochar preparation process comprising a carbonizing furnace, primary leaching tower, secondary leaching tower, a primary water storage tank, a secondary water storage tank, a bio-carbon filtering tank, a high temperature fan and a water pump, where the carbonizing furnace is connected with the high temperature fan and the primary leaching tower via flue gas pipeline. The air outlet of the primary leaching tower is connected with the flue gas pipeline of the secondary leaching tower. The primary and the secondary leaching towers are provided with water inlet and water outlet, where the water inlet is provided with an atomization nozzle. The water outlet is connected with the water collecting pipe of the primary water storage tank. The outlet of the primary water storage tank is connected with the inlet of the bio-carbon filtering tank via pipeline. The bio-carbon filtering pool outlet is connected with a water inlet pipe of the secondary water storage tank through the pipeline. The outlet of the secondary water storage tank is sequentially connected with the water pump and the primary and the secondary leaching tower.