Objective To investigate the correlation between 25-hydroxyvitamin D [25-(OH)D] and disease activity in patients with rheumatoid arthritis (RA). Methods A retrospective study was carried out in the First Hospital of Jiaxing. From January 2015 to December 2018, 456 patients diagnosed with RA and 270 healthy controls were collected. According to different concentrations of 25-(OH)D, they were divided into deficiency group [25-(OH)D < 20?ng/ml], deficiency group [25-(OH)D: 20 to 30 ng/ml] and normal group [25-(OH)D≥ 30?ng/ml]. Tenderness joints count (TJC28), the number of swollen joints count (SJC28) and using DAS28 (ESR) score to assess the RA disease activity were recorded, and then analysis the comparison between 25-(OH)D levels of RA patients with Anti CCP antibody (Anti-CCP antibody, ACPA) positive rate, rheumatoid factor (RF) positive rate, D-Dimer, Ca2+, ESR, SJC28, TJC28 and DAS28 (ESR). Results The 25-(OH)D level of RA patients was significantly lower than that of the healthy control group (P?