Abstract: The red mud(RM), an industrial waste of alumina production, was applied to remove phosphorus from biogas slurry. The XRF, XRD, PSD and SEM tests were employed to assess the physicochemical properties of RM. Some important parameters that affect the phosphorus removal efficiency and final pH of solution(pH_f), such as initial pH(pH_i), RM dosage, reaction time and phosphate concentration of biogas slurry were explored. The results indicated that the phosphate removal efficiency decreased first, and then increased with the increase of pH. And the highest and the lowest phosphate removal efficiency were 89.6% and 47.2%, under the conditions of pH_i 2.1 and 6.9, respectively. The RM dosage and contact time had a positive effect, whereas initial phosphate concentration had a negative effect on phosphate removal and pH_f. The effects of individual variables on phosphate removal were determined by using a 3 ⁴ orthogonal experiment design. The results showed that the optimal reaction conditions were as follows: pH_i 10.0, RM dosage 5.0 g/L, initial phosphate concentration 1.7 mg/L, and contact time 40 min.