Abstract: Objective Study on the effect of phytase on apparent digestibility of crude protein and utilization of calcium or phosphorus in different ages rhesus monkey. Methods Sixteen healthy young and adult breeding rhesus monkeys were selected, and randomly divided into young or adult of treated and control group. Results The apparent digestibility of crude protein were 88.43% ±1.83% and 81.39%±2.28%，in young of treated and control group respectively and the calcium and phosphorus utilization were 61.70% ± 3.70%，84.01% ±2.84%，and 45.32% ± 9.63%，71.15% ± 4.67%，respectively whereas in adult were 89.28% ±1.63% and 81.65% ± 2.95% ,34.18% ± 10.41%,81.97% ±3.38% and 21.18% ± 6.56%，69.23% ± 9.15%. Not only P＜0.05 for the comparison with the control of phosphorus utilization in the adult, but also P＜0.01 of calcium or phosphorus utilization in young group and crude protein apparent digestibility of all. Conclusion The phytase has a good value on utilization of young rhesus monkey.