Abstract: Objective: To investigate the protective effect of phycocyanin on hepatorenal co-damage in mice caused by cyclophosphamide, and to provide new research ideas for evaluating liver and kidney therapy drugs. Methods: Female BALB/c mice were randomly divided into blank group, model group, positive control group, high dose group, middle dose group and low dose group. The hepatic and kindy injury model of mice were established by intraperitoneal injection of cyclophosphamide (50, 100, 200 mg/kg), then the mice of blank group and model group were fed with normal saline, mice of positive control group were fed levimidazole hydrochloride (40 mg/kg) and the mice of dosage groups were fed different dosage of instant power of phycocyanin. Interleukin-2 (IL-2), tumournecrosis factor-α (TNF-α), immunoglobulin (IgG), superoxide dismutase (SOD), malondialdehyde (MDA) of serum in mice, superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) level of liver tissue and superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), uric acid (UA), urea nitrogenin (BUN) level of kindey tissue in each group mice were determined by reagent kit method. Experimental results showed that compared with the model group, the serum levels of IL-2, TNF-α and MDA in mice in the phycocyanin dose group decreased significantly (P<0.01). The high-dose group of phycocyanin significantly reduced serum IgG levels (P<0.05) and increased serum SOD levels (P<0.05). At the same time, it could reduce the elevated content of MDA in mice caused by cyclophosphamide (P<0.01) and increase SOD activity (P<0.05). In addition, the GSH-Px levels of liver tissue in mice in the phycocyanin dose group were significantly higher than those in the model group (P<0.01), while the levels of MDA, ALT, and AST were significantly lower than those in the model group (P<0.01). Compared with liver tissue, the MDA level of mouse kidney tissue in the phycocyanin dose group was significantly lower than that in the model group (P<0.01), the BUN level of mouse kidney tissue in the low-dose phycocyanin group alone was significantly lower than that in the model group (P<0.01), and the UA level of mouse kidney tissue in the high-dose phycocyanin group was significantly lower than that in the model group (P<0.01). So the powder of phycocyanin had protective effect on cyclophosphamide-induced hepatic and kindy injury in mice.