〔Abstract〕 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 ex- pression 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 relat- ed 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 , rheu- matoid 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 (P < 0. 05) , and did not have a correlation with the imaging grading of bone destruction (P > 0. 05) ; multifactor Logistic regression analysis showed that YAP expression was an inde- pendent 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 .