The performance of inorganic sludge separation system is evaluated. Anaerobic digester effluent sludge is used for feed sludge of this system and hydrocyclone is used for inorganic sludge separation. For phosphorus removal and recovery $MgCl_2$ is pumped into MAP growth tank, a component of inorganic sludge separation system. Using this system inorganic sludge which contained less than 40 % of organic matter can be discharged stably and the maximum amount of separated inorganic sludge is 13.4 % of influent sludge based on dry solid. The amount of phosphorus recovered as MAP(as P) is 16.7 % to influent T-P.