Abstract: Modified biochar was prepared using peanut shell as raw material and H₃PO₄ as activator at low pyrolysis temperatures, and its effect and mechanism of Cr（Ⅵ） removal from water were studied. The effects of solution pH, biochar dosage, reaction time and initial mass concentration on the performance of Cr（Ⅵ） removal were investigated, the structure and composition of the modified biochar were characterized by SEM, BET, XPS and FTIR., and analyzed the removal mechanism. The results show that there is no significant difference in the removal effect of Cr（Ⅵ） from modified biochar prepared by low temperature pyrolysis and higher temperature pyrolysis, the low pyrolysis temperature of modified biochar（PBC350） have energy saving and environmental protection advantage. The optimum conditions for the removal of Cr（Ⅵ） by low pyrolysis temperature of modified biochar（PBC350） are initial concentration of Cr（Ⅵ） 100 mg/L, dosage of 0. 10 g in 50 mL solution, pH=2, and reaction time of 8 h. Under the optimized conditions, the Cr（Ⅵ） removal rate reach 99. 0%, which is about 1. 5 times that of unmodified biochar（BC350）. The characterization results show that the surface of PBC350 forms densely honeycomb pore structures, its specific surface area is 17. 75 m~2/g, which is nearly 20 times higher than that of BC350. Moreover, XPS and FTIR results show that PBC350 is successfully doped with P, and introduced a large number of phosphorus containing（P-O） functional groups, which can provide electrons to participate in Cr（Ⅵ） reduction reaction and increase the removal of Cr（Ⅵ）. This study provides a theoretical basis for the application of low temperature pyrolytic phosphoric acid modified biochar in the treatment of heavy metals in wastewater.