Abstract: The purpose of this research is to investigate the effects and mechanisms of paeonol (PL), a phenolic compound found in many traditional Chinese formulations, on reversing drug resistance in the ovarian cancer resistant SKOV3/DDP cells. The results showed that PL had significant drug-resistant reversal effect on SKOV3/DDP cells. Flow cytometry showed that PL could inhibit P-glycoprotein (P-gp) function in a concentration-dependent manner. Fluorescent quantitative PCR and cell immunofluorescence techniques were used to detect mechanisms of action. Results revealed that both the inhibitory effect on MDR1/P-gp and metadherin (MTDH) expression and the induction effect on phosphatase and tensin homolog (PTEN), by 15, 30, and 60 μmol·L^-1 PL, were increased with increased concentrations of PL (P < 0.01, P < 0.05). The inhibitory effect on MTDH mRNA and the induction effect on PTEN mRNA, by PI3K inhibitor LY294002, were stronger or equivalent to that of the 60 μmol·L^-1 PL treated group; however, the inhibition or induction effect on MTDH or PTEN protein were only comparable to the 15 μmol·L^-1 PL treated group. The present study shows that the effect of PL on SKOV3/DDP cells may be related to the inhibition of P-gp function and expression, the inhibition of MDR1, MTDH expression, and the induction of PTEN expression, all which can provide a theoretical foundation for PL as a drug resistance reversal agent on the treatment of ovarian cancer chemotherapy resistance.