Objective The plasma levels of fibrinogen degradation products (FDP),D-dimer(DD) and fibrinogen (Fg) in patients with rheumatoid arthritis (RA) were tested and the relationship between the upregulated coagulation system and disease activity were explored.Methods Patients were divided into the active group and the remission group and 50 patients were included in each group.Hematological variables,including FDP,DD,Fg,and disease activity parameters including erythrocyte sedimentation rate (ESR),C-reactive protein (CRP) levels and rheumatoid factor (RF) titer were measured.Two-sample t-test,linear correlation test and Chi-square test were nsed for data analysis by SPSS 11.0 software.Results Age and sex were comparable in the two groups (P＞0.05).The FDP,DD and Fg were significantly higher in patients with active disease [(12.0±8.2) μg/ml, (3.1±3.1) μg/ml, (4.6±1.4) g,/L] than those in patients with remission [(2.1±1.1) μg/ml, (0.4±0.4) μg/ml, (3.0±0.6) g/L,all P＜0.01 ].There was no difference in gender distribution in FDP and DD (P＞0.05).However,Fg was significantly higher in men than that in women (P＜0.05).FDP showed a significantly positive correlation with DAS28 (r=0.48,P＜0.01) and ESR(r=0.28,P＜0.05).DD correlated positively and significantly with ESR and DAS28 (r=0.69,0.52,all P＜0.01).Fg was significantly positively correlated with DAS28,CRP and ESR (r=0.57,0.64,0.68,all P＜0.01).FDP,DD and Fg were not correlated with RF (r=-0.07,0.06,-0.01,all P＞0.05).Conclusion FDP and DD correlate well with disease activity and may be important disease activity parameters for RA.The rank of sensitivity of FDP,CRP,DD,ESR,Fg and RF for disease activity assessment of RA presents in a declined manner.