The invention provides an external prescription for treating gynecological diseases. The prescription comprises the following components by weight: 1-10g of gallnut, 1-15g of dandelion, 1-20g of sophora flavescens, 1-30g of cortex phellodendri, 1-40g of lance atractylodes rhizome, and 1-50g of mint. The preparation method comprises the following steps: removing impurities, washing, baking, grinding, sc reening and uniformly mixing; or powdering the components, mixing the gallnut, the dandelion, the cortex phellodendri, the sophora flavescens, dried alum and mint to form a powder preparation, and packaging into bags or bottles to prepare suppository. The external prescription can be used for treating gynecological diseases, such as uterine erosion and various inflammations, and can prevent cancerization.