Abstract: The impact of coagulation on enhancing microalgae sedimentation was probed to offer technical support for the treatment of ionic rare earth mine wastewater using microalgae. The influences of polyacrylamide concentration, flocculation reaction time, flocculation stirring speed, and algal density on effluent algal density and turbidity in algae solution from a photo reactor were analyzed. With the escalation of PAM concentration, the algae density and turbidity of the supernatant initially decreased and then tended to stabilize. When the PAM concentration rose to 15 mg/L, the algae density and turbidity of the supernatant tended to stabilize. With the increase in stirring speed, the turbidity of the supernatant decreased initially and then tended to stabilize, but it exerted little influence on the algae density of the supernatant. With the elongation of the stirring time, the algae density and turbidity of the supernatant decreased initially and then stabilized. The turbidity of the supernatant fluctuated in stages with the increase in algal density, and the algae density of the supernatant displayed no obvious change pattern.