The invention relates to a preparation method of a szechwan Chinaberry fruit oil transdermal agent. The method comprises the following steps: (1) successively dissolving szechwan Chinaberry fruit oil in anhydrous ethanol and distilled water; (2) heating to prepare a chitosan glacial acetic acid solution; (3) mixing a traditional Chinese herbal extract with the chitosan glacial acetic acid solution; (4) adding the mixture into an emulsification system for emulsification; (5) conducting a cross-linking reaction on the emulsion products; and (6) treating the crosslinking products by washing, precipitation, centrifugation and drying to obtain a transdermal medical membrane loaded with traditional Chinese herbal extract. The preparation method is simple, and suitable for large-scale industrial production.