Abstract: The fresh blue-green algae in algae bloom were used for treatment and the crude extracts of phycocyanin were obtained by freeze-thaw method. On the basis of single-factor experiment of salt precipitation in the first and second steps, salt precipitation time, the impacts of phycocyanin concentration, pH and (NH₄)₂SO₄ saturation on the purifying phycocyanin were comprehensively considered using the orthogonal experiment. The results showed that the optimum conditions in the first step were 17% of (NH₄)₂SO₄ saturation, 1.45 g/L of crude phycocyanin extract, pH 6.4 and 15 min of reaction time. In the second step, the optimum (NH₄)₂SO₄ saturation was 35%, with pH 4.0 and 15 min of reaction time. The purity of phycocyanin was 2.04 at last, which would facilitate further purification.