OBJECTIVE： To prepare zolmitriptan-diclofenac microemulsion， and conduct quality evaluation and in vitro transdermal study. METHODS： Using solubility and microemulsion area in pseudo-ternary phase diagram as indexes， the types of oil phase and mixed emulsifier ratio of zolmitriptan-diclofenac microemulsion were screened； the microemulsion quality was inspected using particle size， Zeta potential， appearance and stability. HPLC was used to measure the contents of zolmitriptan and diclofenac. Transdermal diffusion test instrument was used， 2 g microemulsion was smeared in cuticle of extracouporeal rats’ skin， and cumulative transdermal rate in 24 h was determined. RESULTS： The microemulsion formulation was as follow as 10％ oil phase （octanoic acid triglyceride）， 25％ mixture emulgator [polysorbate 80-brij 97 （1 ∶ 1）]， 8.3％ propylene glycol and 25 mg zolmitriptan， 1.25 mg diclofenac， and water adding to 100 mL. The average particle size of prepared microemulsion was （28.2±2.5） nm， Zeta potential was （－3.25±0.33） mV， the appearance was rounding； the microemulsion showed no stratification or flocculation at room temperature after placed for 1 month. Contents of zolmitriptan and diclofenac were 0.248 mg/mL， 12.46 mg/mL （n＝3）； 24 h cumulative transdermal rates were 80％， 75％. CONCLUSIONS： Zolmitriptan-diclofenac microemulsion is prepared， and its in vitro transdermal ability is good.