Abstract: Objective To study the effects of deep sea fish oil supplimentation on clinical manifestation and eryth rocyte sedimentation rate(ESR)among Chinese rheumatoid arthritis(RA)patients.Methods In a placebo-controlled,double-blind prospective study,60 RA patients were randomly allocated to consume a daily nutritional supplement of 6 gram oil capsules containing either soybean oil and deepsea fish oil(eicosapentaenoic acidEPA1.8 g+docosahexaenoic acidDHA1.2 g)for 12 weeks.Anthropometry and ESR were measured.Visual analogue scale(VAS),disease activity score(DAS),and health assessment questionnaire(HAQ)were used in the study.Results There were significant differences in intakes of polyunsaturated fatty acid(n-6 polyunsaturated fatty acidn-6 PUFA ,n-3 PUFA,n-6/n-3PUFA,linoleic acidLA,linolenic acidALA,EPA and DHA)between the two groups(P < 0.01 for all).VAS(76.17±2.78)was significantly increased in fish oil group(t=-2.023,P=0.048),while DAS28(3.41±0.13,t=2.434)and ESR 17(7.50,52.00,Z=-2.012)were reduced(P_DAS28=0.018,P_ESR=0.044).Conclusion Fish oil(1.8 g EPA⁺1.2 g DHA)/per day for 12 weeks)is beneficial to patients with RA.Dietary intervention maybe has long-term effects on RA patients.