The invention discloses an extraction-separation method and an application of corilagin. The method comprises the steps of treating longan kernel powder once by using anhydrous acetone and extracting by using acetone aqueous solution again for the second time; uniformly mixing a proper amount of chromatography polyamide with the acetone aqueous solution, recycling acetone and applying to a polyamide chromatography column; eluting by sequentially using pure water, methyl alcohol aqueous solutions with different concentrations and methyl alcohol; gathering 40-60 percent of methyl alcohol eluant in a separate bottle form, condensing and separating out corilagin crystals; mixing mother liquid with the rest of eluant containing corilagin, condensing to be dry, dissolving into methyl alcohol and applying to a polydextran gel LH-20 column; eluting by methyl alcohol; gathering eluant in a separate bottle form and standing; mixing with the eluants in which corilagin crystals are separated out; standing again until the orilagin crystals which are separated out are not increased; mixing the obtained corilagin crystals with corilagin crystals obtained by chromatography polyamide; performing recrystallization by using ethyl alcohol to obtain corilagin with high purity. The corilagin subjected to extraction and separation has a function of inhibiting tyrosinase.