Abstract: The research was conducted to determine the optimum dose of phytase supplementation of Fusarium verticillioides on Phosphor-deficient rations. This study used 24 broiler chickens (4 weeks). This research used Completely Randomized Design (CRD) with five ration treatments with 4 replications. Ration treatment was supplemented phytase with different doses: R1: 0 U/kg, R2: 250 U/ kg, R3: 500 U/kg, R4: 750 U/kg and R5: 1000 U/kg. Ration was based on iso protein (20%) and iso energy (2882 kcal/kg). The variables measured were retention of phosphor, calcium and nitrogen. The results showed that supplementation of phytase on broiler rations which Phosphor-deficiency was influenced the retention of Phosphor, calcium and nitrogen significantly (P<0.01). The optimum phytase supplementation of Fusarium verticillioides on broiler rations which phosphor-deficient was 750 U/kg ratio, it is seen from retention of phosphor (71.38%), calcium (75.65%) and nitrogen (67.61%).