The invention discloses sodium valproate-containing sustained-release transdermal patch as well as a preparation method and application thereof. The sustained-release transdermal patch comprises a back lining layer, a medicine-containing layer and a protective layer, wherein the medicine-containing layer comprises sodium valproate, a complexing agent, an adhesive, a transdermal improver, a bacteriostatic agent and a hot-melt pressure-sensitive adhesive. The preparation method comprises the following steps: heating and melting the hot-melt pressure-sensitive adhesive, adding the sodium valproate, the transdermal improver, the adhesive, the complexing agent and the bacteriostatic agent into the hot-melt pressure-sensitive adhesive to dissolve, mixing uniformly, performing ultrasonic degassing, coating the surface of the protective layer with the mixture to form the medicine-containing layer, and covering the surface of the dried medicine-containing layer with the back lining layer; cutting and packaging. The sodium valproate-containing sustained-release transdermal patch can serve as a medicine for treating pediatric epilepsy. The sodium valproate-containing sustained-release transdermal patch has medicine release uniformity and mild and durable effect, can effectively reduce the administration times, is convenient in dosage adjustment, is convenient to carry, has high patient adaptability, and solves the problem that infantile administration is difficult.