Synthesis of a new heavy metal collector（or heavy trap） N-methylene base lignin-N′-dithiocarbamic acid hexame thylene diamine salt（Lig-DTC） with alkali lignin as matrix by Mannich reaction and carbon disulfide addition，used to chelate heavy metals in arseniccontaining acidic wastewater，precipitated by flocculation，and the treated acidic water can be reused.Taking the residual mass concentration of heavy metal ions in acid wastewater as the evaluation standard，the factors such as dosage of the heavy trap，reaction time，pH of the solution and the dosage of the flocculant were investigated by orthogonal experiment and single factor experiment.The best process conditions（based on 100 mL wastewater） were obtained as follows: the dosage of Lig-DTC was 60 mg，the reaction time was 15 min，the dosage of polyacrylamide（anionic PAM，mass fraction of 0.1%） was 1.1 mL and the rest time was 30 min without adjusting the acidity of wastewater.Under this conditions，the residual heavy metal ion mass concentration met the processing requirements，and the acidic wastewater can enter the system cycle.