The invention relates to a triangular support leg of a miniature drilling machine for a rock bolt of an overhead power transmission line. The triangular support leg comprises a triangular disc, disc nails, a plugging fixing clamp and a connecting ring, wherein the bottom surface of the triangular disc is provided with the disc nails, the triangular disc is provided with a through hole, the plugging fixing clamp penetrates through the through hole, the connecting ring is arranged above the triangular disc, the three edges of the triangular disc are respectively provided with a foldable plate, each foldable plate is provided with an auxiliary through hole, and auxiliary plugging fixing clamps penetrate through the auxiliary through holes. The triangular support leg has the advantages that the triangular support leg is mainly applied to a bracket of the miniature drilling machine for the rock bolts of various overhead power transmission lines, and the stable construction and drilling of the miniature drilling machine for a rock bolt foundation are guaranteed.