NOVELTY - A flue gas complex absorption combined aerobic denitrification and denitration method involves placing alkaline absorption liquid and cobalt complexing agent in an absorption tower, regenerating the cobalt complexing agent, performing aerobic denitrification process, completely eliminating nitrogen pollution, passing residual liquid into a depositing pool, depositing active sludge, returning separate liquid into absorption tower, mixing the cobalt complexing agent with inorganic cobaltous salt and ligand, controlling pH value of an aerobic bioreactor between 6.0-9.0 for 6-36 hours at 25-35 degrees C.    USE - Method for complex absorption combined aerobic denitrification and denitration of flue gas.    ADVANTAGE - The method enables complex absorption combined aerobic denitrification and denitration of flue gas with reduced nitrogen pollution, and reduced energy consumption, in cost effective manner.    DETAILED DESCRIPTION - A flue gas complex absorption combined aerobic denitrification and denitration method involves placing alkaline absorption liquid and cobalt complexing agent in an absorption tower to transfer nitric oxide and oxygen from liquid phase, regenerating the cobalt complexing agent, discharging air in purification standard, passing alkaline absorption liquid in an aerobic bioreactor under neutral condition, performing aerobic denitrification process, completely eliminating nitrogen pollution, passing residual liquid into a depositing pool, depositing active sludge, returning separate liquid into the absorption tower, mixing the cobalt complexing agent with inorganic cobaltous salt and ligand, where inorganic cobalt salt comprises ferrous chloride, cobalt sulfate, cobalt nitrate and ferrous cobalt and ligand comprises ethylene diamine tetraacetic acid, citric acid, nitrilotriacetic acid, hydroxyethyl ethylenediamine triacetic acid, ethyl triamine penta acetic acid, controlling pH value of the aerobic bioreactor between 6.0-9.0 for 6-36 hours at 25-35 degrees C.