The work aims to treat package and printing wastewater by phosphoric acid modified biocarbon to explore a new way for optimum utilization of straw biomass. The biocarbon was modified by phosphoric acid. The optimum process condition was found by orthogonal experiment. The phosphoric acid modified biocarbon for package and printing wastewater treatment was prepared with the optimum process condition. The effects of phosphoric acid modified biocarbon dosage, adsorption time and pH value on adsorption capacity, COD removal rate and decolourization rate of package and printing wastewater were researched. The optimum process condition of biocarbon modified by phosphoric acid was that: phosphoric acid volume fraction was 40%, modified time was 4 h, modified temperature was 40 ℃. The optimum process condition of phosphoric acid modified biocarbon for package and printing wastewater treatment was that: adsorption time was 60 min, pH value was 8, phosphoric acid modified biocarbon dosage quality concentration was 0.3 g/L. Biocarbon modification by phosphoric acid can improve the adsorption capacity of pollutants. It can be used to absorb pollutants package and printing wastewater in the preliminary treatment.