Objective:To compare the clinical characteristics, clinical efficacy and adverse drug reactions of rheumatoid factor (RF) positive (+ ) and negative (-) polyarticular juvenile idiopathic arthritis (PJIA).Methods:The clinical data of 67 PJIA patients admitted into Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, from January 2013 to December 2018 were analyzed retrospectively.They were divided into RF-positive PJIA group [RF (+ ) group, 23 cases] and RF-negative PJIA group [RF (-) group, 44 cases] according to RF titer.The clinical characteristics, laboratory indexes and clinical efficacy evaluation of the two groups were compared.Results:(1)Distribution of affected joints: the top 3 affected joints in the RF (+ ) group were the knuckles (16 cases, 69.57%), the wrists (15 cases, 65.22%) and the ankles (13 cases, 56.52%), and those in the RF (-) group were the knees (33 cases, 75.00%), ankle joints (29 cases, 65.91%) and hip joints (26 cases, 59.09%). The wrist joint involvement of the RF (+ ) group was significantly higher than that of the RF (-) group, while the knee joint involvement was lower than that of the RF (-) group.The difference was statistically significant (all P<0.01). (2)Magnetic resonance changes of the affected joints: articular cavity effusion (54 cases, 84.38%), synovial thickening (44 cases, 68.75%) and bone edema (26 cases, 40.63%) are common in both groups.The incidence of bone destruction (7 cases, 70.00%) and soft tissue edema (7 cases, 70.00%) in the RF (+ ) group was higher than that in the RF (-) group (2 cases, 18.18% and 2 cases, 18.18%), the difference was statistically significant (all P<0.05). (3) Changes in laboratory indicators: the positive rates of C-reactive protein, erythrocyte sedimentation rate, anti-cyclic citrullinated peptide antibody and anti-nuclear antibody in the RF(+ ) group were significantly higher than those in the RF(-) group, the difference was statistically significant (all P<0.05). (4)Juvenile arthritis disease activity score 27 (JADAS27): the score difference between RF(+ ) group and RF(-) group was not statistically significant [(22.83±5.60) scores vs.(23.07±6.66) scores, t=0.148, P>0.05]. (5) Efficacy analysis: 2 patients were lost to follow-up after discharge, and the remaining 65 patients were treated with traditional therapy, of which 30 were given biologics at the first hospitalization, 9 cases were treated with biologics after the failure of traditional treatments, and 35 patients were treated with biologics to control disease activity.In different dosage regimens, the disease remission rate in the RF(-) group is generally higher than that in the RF(+ ) group. Conclusions:PJIA patients have complicated joint involvement, RF-positive patients are more prone to joint destruction, and traditional treatments are less effective.Biological agents can effectively improve the symptoms of severe PJIA patients, especially those with poor prognosis.