This study investigated the treatment efficiencies of phosphorus wastewater by precipitation process. The removal of phosphorus by adding waste lime from highly polluted water with various phosphorus concentration were studied in a batch reactor. The batch reactors were fed synthetic wastewater. optimum operating conditions for precipitation process were pH 7.1 with dosage of waste lime and Al₂(SO₄)₃ being 4g/L and 4g/L, respectively. Phosphorus removal efficiency was about 99% in the precipitation process.