The invention discloses an eprinomectin transdermal agent, a preparation method and application. The eprinomectin transdermal agent is composed of azone, oleic acid, propylene glycol, dimethyl sulfoxide and alcohole with a certain weight amount. The preparation method comprises: A, performing sample preparation, namely, setting five levels for each transdermal promoting agent, and adding alcohol for preparing samples; B, performing in-vitro transdermal experiments, fixedly disposing skin of a white mouse between a dispersion pool and a receiving pool of a YB-P6 intelligent transdermal tester, enabling the inner layer surface of skin to face to the receiving pool, enabling the whole dispersion pool to be full with the eprinomectin transdermal-agent formula sample, and adding acetonitrile to fill the receiving pool as a receiving solution; C, detecting the receiving solution obtained in the step B by using high performance liquid chromatographic instrument, and selecting a formula through visual analysis and variance analysis on an orthogonal experiment result; D, preparing the formula and verifying according to the front steps; and E, preparing a final product, and preparing a transdermal agent containing 0.025-0.1 g of eprinomectin. The formula is reasonable, convenient to use and capable of continuously expelling parasites without needing withdrawal time, and has the expelling rate of 90% or more on nematode and ectoparasites.