The invention relates to a hot-stamping forming die insert structure and a machining method thereof. The insert structure comprises a water inlet channel, a drainage channel, a supporting block and aforming block, the forming block comprises a baroque structural plate corresponding to a stamped workpiece forming structure, the outer side face of the baroque structural plate is a stamping workingsurface, and the inner side face of the baroque structural plate is a cooling water forming surface, the supporting block is located on the side where the cooling water forming surface is located, theend face, facing the cooling water forming surface, of the supporting block is a baroque surface corresponding to the cooling water forming surface, a gap is formed between the baroque surface and the cooling water forming surface, and a baroque cooling water area is formed, a plurality of supporting columns are arranged on the baroque surface in a dot matrix mode, and the free ends of the supporting columns abut against the corresponding cooling water forming surface; and the water inlet channel and the drainage channel both communicate with the baroque cooling water area. According to the hot-stamping forming die insert structure, the contact area of cooling water and the die working surface is ensured to the maximum limit, thus the cooling effect is ensured, the heat exchange effect isbetter, the cooling efficiency of a hot stamping die is significantly improved, and the heat treatment effect of the stamped workpiece is ensured.