〔Abstract〕 Objective To investigate the differential expression of Yes-associated protein(YAP) in the healthy control group and in patients with rheumatoid arthritis(RA), and to explore its correlation with the progression of the disease. Methods Three cases each of synovial membranes from the healthy control group and RA group were selected for RNA-sequence detection to identify differentially expressed genes. Data and laboratory indicators from 50 healthy control cases and 150 RA patients who met the criteria were collected. ELISA was used to detect the expression of YAP in the serum of each group, and then its correlation with other laboratory indicators in RA patients was analyzed. The receiver operating characteristic curve was applied to explore the diagnostic efficacy of the related risk factors for RA. Results Expression of 14-3-3-gama, which regulated the disease process, was significantly down-regulated in the synovial membranes of RA patients compared to normal synovial membranes; YAP expression was significantly up-regulated in rheumatoid arthritis fibroblast-like synoviocytes compared to healthy controls and was correlated with haematological sedimentation, C-reactive protein, interleukin(IL)-1, IL-4, IL-6, IL-10, rheumatoid factor, anti-cyclic citrullinated polypeptide antibody, interferon alpha, tumour necrosis factor alpha, protein electrophoresis α1 globulin, protein electrophoresis alpha2 globulin, disease activity scores, disease activity index, and patient-reported outcome had correlations(P0.05); multifactor Logistic regression analysis showed that YAP expression was an independent influencing factor for the prognosis of RA patient. Conclusion YAP is differentially expressed between the healthy control group and RA group, which shows a significant positive correlation with the disease activity of RA, potentially becoming a new target for clinical treatment of RA.