Objective To explore the application and clinical significance of interleukin 17 (IL-17), peripheral blood platelet/lymphocyte ratio (PLR) and rheumatoid factor (RF) in the diagnosis of rheumatoid arthritis (RA). Methods A total of 78 RA patients who were hospitalized in the hospital from June 2017 to December 2019 were enrolled as study group. According to the disease activity score 28 (DAS28), they were divided into active stage group (30 cases) and remission stage group (48 cases). And 78 healthy people were enrolled as control group. The levels of serum IL-17, PLR and RF in all patients were recorded. And their application and clinical significance in the diagnosis of RA were analyzed. Results The levels of IL-17, PLR and RF in study group were higher than those in control group (P<0.05), which were higher in active stage group than remission stage group (P<0.05). ROC results showed that AUC values of IL-17, PLR, RF and their combination for diagnosis of RA were 0.800, 0.878, 0.854 and 0.964, respectively. AUC of combined diagnosis was higher than that of single index (P<0.05). Conclusion The detection of serum IL-17, PLR and RF levels can reflect disease progress, and their combination improve diagnosis accuracy rate of RA, which is of important clinical value in the diagnosis and treatment of RA patients.