【Abstract】Objective To investigate the correlation between serum solube suppression tumorigenicity2 (sST2) and disease activity in patients with rheumatoid arthritis (RA). Methods 128 patients with RA (RA group) who were treated at the hospital between October 2018 and October 2019 and 100 healthy people (the control group) who came to the hospital for physical examination during the same period were selected as the research subjects. Serum sST2, rheumatoid factor (RF), interleukin33 (IL33) and anticyclic citrullinated peptide (CCP) antibody levels were measured, and the disease activity of RA group was evaluated. Serum index levels of the two groups were compared, and the value of serum sST2 level in diagnosis of RA was analyzed. Serum index levels of RA patients with different disease activities were compared, and the relationship between sST2 level and other serum indexes and disease activity was analyzed. Results sST2, RF, IL33 and antiCCP antibody levels in RA group were significantly higher than those in control group (P＜005). ROC curves showed that the optimal cutoff value of sST2 was 24.65ng/mL, and the corresponding sensitivity, specificity and AUC were 862%, 824% and 0865 (95%CI: 0663~0972, P＜005). For patients with RA, sST2, RF, IL33 and antiCCP antibody levels in remission group, low activity group, moderate activity group and severe activity group increased in sequence (P＜005). Pearson correlation analysis showed that sST2 level was positively correlated with RF, IL33 antibody, antiCCP antibody and DSA28 scores (P＜005). Conclusion Patients with RA have abnormally elevated serum sST2 levels, which can be used for diagnosis of RA. Additionally, the level is closely related to disease activity.