Abstract: In the present study, extraction process and antitumor activity of polysaccharide extracted from the Rosa roxbunghii Tratt (RRT) dried fruit were studied. The extraction technology of Rosa roxbunghii Tratt polysaccharide (RRTP) was optimized by mono-factor experiments and response surface methodology, and the antitumor activities of RRTP were studied by the model of S₁₈₀ solid tumor. The results showed that the optimum extraction conditions for RRTP as follows: Enzymatic hydrolysis pH6.2, enzymatic hydrolysis time 4 h, enzymatic hydrolysis temperature 41 ℃, enzyme dosage 1.62%, liquid-solid ratio 30:1 mL/g, and then extracted at 90 ℃ hot water for 3 h after enzymatic hydrolysis completed. The yield of RRTP was 6.32%±0.12% on average under the optimum processing conditions. Furthermore, antitumor activity analysis showed that RRTP had obvious antitumor activity and could significantly (P<0.05) increase leukocyte count, thymus index and spleen index in S₁₈₀ solid tumor mice. And the result indicated RRTP had a tumor inhibitory rate of 52.13%±1.84% in S₁₈₀ solid tumor mice with gastric irrigation dose at 200 mg/kg. It was concluded that RRTP could improve the immune function and antitumor of S₁₈₀ solid tumor mice, and could be used as a potential functional food supplements or natural substances of antitumor drugs.