Abstract: In this study, the effect of p H and microemulsion excipients on the stability of resveratrol were examined.First, solutions containing equivalent resveratrol with various p H were prepared.Then resveratrol- excipient solutions were formulated, in which resveratrol was either mixed with oil phase, emulsifier, and co- solvent, separately, or blended with them together.The test solutions were placed under 40 ℃ and assayed at specific intervals.Curves of concentration versus time were fitted by sorts of dynamic equations, respectively, from which constants of degradation rate were calculated. The results showed that stable p H range of resveratrol was 3.6 to 5.0. Though microemulsion excipients accelerated degradation of resveratrol when they were mingled with the ingredient separately, the mixture could make resveratrol decomposition slower. Some excipient mixture even improved resveratrol stability.The appropriate emulsifier and co- solvent for resveratrol microemusion were cremophor EL and polyethylene glycol 400, respectively.