Abstract: Experiments on treating high-concentrated refractory organic wastewater from banknote printing works by organo-modified bentonite were performed to degrade the organic pollutants and color. The most important factor in the experiments is the dosage of poly aluminum chloride (PAC). When the dosages of organo-modified bentonite and PAC are 15 and 3. 5 g·L^-1, respectively, and the mixing time is 0. 5 h, the treatment effect achieves the best level. The absorbance removal rate of the wastewater can reach up to 98. 11%, while the removal rate of chemical oxygen demand (COD) increases to 73. 31%. This treatment can dissolve COD and color in the wastewater without producing the concentrated wastewater and inviting any toxic and harmful substances, so it is a favorable pretreatment for an advanced wastewater treatment.