Abstract： Objective To investigate the correlation of expression of soluble triggering receptor expressed on myloid cells-1 ( sTREM-1 ) in the sera with the activity of rheumatoid arthritis(RA).Methods All 80 RA patients ( 15 remissive and 65 active) and 74 normal controls were enrolled in the study.Enzyme linked immunosorbent assay (ELISA) was applied to detect sTREM-1 in the sera from RA patients and normal controls.The correlation of sTREM-1 with medical history,painful joint count,swollen joint count,erythocyte sedimentation rate,highsensitivity C-reactive protein,rheumatoid factor and anti-cyclic citmllinated peptide antibody were observed.Results The level of sTREM-1 in RA patients was higher than that in the normal ones and the difference had a statistical significance [ ( 3.2 ± 1.3 ) μg/L vs (2.6 ± 1.4 ) μg/L,r =2.94,P ＜ 0.05 ].The level of sTREM-1 in active RA patients was higher than that in the remissive ones [ ( 3.3 ± 1.2 ) μg/L vs (0.9 ± 0.6 ) μg/L,r =4.50,P ＜0.05 ].The sTREM-1 level in patients with X-ray damage of hands joint was higher than that in patients with non-X-ray damage of hand joint[ (3.7 ±1.1) μg/L vs (2.5 ± 1.1) μg/L,r =4.52,P＜0.01 ].There was a significant association between sTREM-1 level and DAS28 score,swollen joint count,erythrocyte sedimentation rate,rheumatoid factor and anti-cyclic citrullinated peptide antibody in RA patients ( r1 =0.8500,r2 =0.6412,r3 =0.8263,r4 =0.4421,r5 =0.6635,all P ＜ 0.01 ).Conclusions Level of sTREM-1 are high in sera of RA patients.Positive correlation with DAS28,the number of swollen joints,erythrocyte sedimentation rate,rheumatoid factor,anti-cyclic citrullinated peptide antibody and Serum sTREM-1 may be indicators of disease activity.