Objective To explore the effect of CCR5 siRNA on the proliferation and cell cycle of synoviocytes in rats with rheu-matoid arthritis（RA）and its possible mechanism by inhibiting the expression of CCR5 with small interfering RNA（siRNA）. Methods An RA rat model was constructed by collagen induction method. Synoviocytes of the RA rats were isolated and cultured，in which CCR5 siRNA and negative control（NC）siRNA vectors were then transfected by Lipofectamine 2000 to determine the transfection effi-ciency. The synoviocytes cultured in vitro were divided into four groups: RA group（synoviocytes of RA rats），RA+NC group（with lipo-some-encapsulated NC siRNA），RA+mock group（with liposome），and RA+siRNA group（with liposome-encapsulated CCR5 siR-NA）. After the expression of CCR5 in the synoviocytes of RA rats was inhibited by RNA interference technology，qRT-PCR and West-ern blot were used to measure the mRNA and protein expression of CCR5 and cell cycle-related genes（Cyclin D1，Cyclin E1，and Cy-clin B1）in each group. The proliferation and cell cycle distribution of synoviocytes in each group were determined by MTT and PI stain-ing，respectively. Results Compared with the RA group，the RA+siRNA group showed significantly reduced CCR5 mRNA level（1.16 ± 0.21 vs 1.85 ± 0.61）and CCR5 protein level（0.19 ± 0.01 vs 0.44 ± 0.05）（P < 0.05）. The mRNA levels of Cyclin D1，Cyclin E1， and Cyclin B1 in the RA+siRNA group（1.32 ± 0.01，1.23 ± 0.26，and 1.33 ± 0.05，respectively）were significantly decreased as com-pared with those in the RA group（1.52 ± 0.06，1.68 ± 0.08，and 1.94 ± 0.07，respectively）（P < 0.05）. The protein levels of Cyclin D1， Cyclin E1，and Cyclin B1 in the RA+siRNA group（0.88 ± 0.03，1.46 ± 0.13，and 1.56 ± 0.13，respectively）were significantly lower than those in the RA group（1.38 ± 0.03，1.98 ± 0.12，and 2.13±0.08，respectively）（P < 0.05）. Compared with the RA group，the RA+ siRNA group showed an increased G0/G1 phase ratio of synoviocytes（70.27% ± 1.06% vs 59.26% ± 0.59%，P < 0.05）and a decreased S phase ratio of synoviocytes（14.10% ± 0.82% vs 23.94% ± 1.71%，P < 0.05），as well as significantly inhibited growth of synoviocytes， but there were no significant differences in the RA+mock and RA+NC groups（P > 0.05）. Conclusion CCR5 gene silencing can inhib-it the growth of synoviocytes，manifesting as increasing the G0/G1 phase ratio of synoviocytes and decreasing the S phase ratio. The cell cycle distribution can be regulated by regulating the expression of cell cycle-related genes（Cyclin D1，Cyclin E1，and Cyclin B1），thus affecting the proliferation of synoviocytes.