ObjectiveTo investigate the effect of protein on growth and serum biochemical indexes of juvenile Tibetan macaqueb by a ninety-day feeding trial. MethodDiets with five levels of protein (11.1%, 16.1%, 20.5%, 24.5% and 29.8%) were fed to Tibetan macaque. The results showed that:weight gain, serum albumin, globulin increased with the increasing protein levels (P<0.05). ResnltsActivities of serum aspartate aminortransferase, alanine aminotransferase and urea nitrogen were significantly improved in response to the increasing levels of dietary protein. But there was no significant difference in serum total protein, triglycerides, Gamma-irradiation glutamine shift enzyme and alkaline phosphates among these groups. The dietary protein requirement for weight gain of juvenile Tibetan macaque pestimated by brokenline model was 23.69%.ConclusimUnder the cage conditions the 23.69% protein is the best choice considering animal biology and feed expense.