The invention discloses a multi-layer high gradient insulator for a high-voltage pulse power supply and a manufacturing method thereof. The multi-layer high gradient insulator is characterized in that thin conductive layers are regularly embedded in an insulator body made of an insulated material, the side surface of the insulator, which is in a certain depth, is formed by an insulated material layer and a conductive material layer, and the interior of the insulator is formed by a single insulated material. According to the invention, a conductive array is embedded in the side surface of the insulator body, the secondary electron emitting characteristic of the surface of the insulator and the surface load charge accumulation are restrained, the vacuum surface flashover characteristic of the insulator body is improved, the surface impact voltage of the insulator body is improved, the problem that the insulated material layer is not matched with the mechanical and thermal performance of the conductive material layer is solved, and the process difficulty and cost for manufacturing the multi-layer high gradient insulator are remarkably lowered.