The aim of experiment was to investigate the effects of different levels of green tea powder on immunological function in aged canines. Seventy two ten year-old aged canines with an average body weight of 34.5~37.5 kg were randomly allocated into 4 groups with 3 replicates of 6 canines, four diets containing green tea powder (0, 1 000, 2 000, 4 000 mg/kg) were given to feed the canine for 9 weeks. The results indicated that containing green tea powder (2 000 mg/kg) group T Lymphocyte Transformation Rate(LTT) reached the highest, increased significantly (P<0.05) up to 47.83%. Although lower adding green tea powder (1 000 mg/kg) reduced serum lysozyme activity in the aged canine, but not significantly (P<0.05), and 2 000 mg/kg and 4 000 mg/kg groups serum lysozyme activity in aged canine were increased obviously (P<0.01). Compared with control the contents of lysozyme in the 2 and 3 treatments increased 32.76% and 19.39% respectively. At the same time, that addition of green tea powder, the total protein(TP) in blood were slightly higher than those in control (P>0.05). When the levels of green tea power increased, the contents of globulin increased. Treatment 3(4 000 mg/kg) were higher than those in the control group(P>0.05).