Abstract: Objective To study the effect of paeoniflorin (PF) on mTOR signal in synovial fibroblast-like synoviocytes (FLS) in rats with adjuvant arthritis. Methods AA model rats were prepared by complete Freund's adjuvant injection in foot-plantar, the PF was injected to rats in AA + PF 100 μg/mL group, AA + PF 200 μg/mL group and AA + PF 400 μg/mL group by the tail vein injection at the dose of 0.1 mL/200 g body mass, and the effects of three doses of PF on arthritis scores in AA rats were studied. The modeling rats and control rats were sacrificed at 28 d after modeling, then the synovium was separeated from rat articular, the FLS were cultured. The effect of PF on the expression of mTOR and MMP3 in AA FLS was detected by the real time qPCR. The effect on the cytokine IL-1, IL-6 was detected by ELISA, and the Western blot was used to investigate the role of PF in the mTOR phosphorylation. Furthermore, FLS were transfected with mTOR vectors, and the effect of mTOR overexpression on the PF roles was detected by real time qPCR and ELISA. Results The tail vein injection of PF can significantly reduce the AA rat arthritis score. Compared with AA group, the expression of mTOR in AA+PF 1 μg/mL, AA+PF 2 μg/mL, AA+PF 4 μg/mL was significantly decreased at 48 h after dosing. Compared with AA group, the relative expression of p-mTOR protein in PF 2 μg/mL group was also decreased. Compared with AA group at 48 h after dosing, the levels of IL-1, IL-6 and MMP3 in AA+PF 1 μg/mL, AA+PF 2 μg/mL, AA+PF 4 μg/mL were significantly decreased, respectively. Compared with PF 2 μg/mL group, the relative expression of IL-1, IL-6 and MMP3 in PF 2 μg/mL+mTOR vectors was increased. Conclusion PF can significantly inhibit the pathology of AA rats, and its mechanism may be related to the inhibition of mTOR signal in FLS of AA rats.