The utility model provides a wall tube insulator, related to power transmission and distribution equipment, in particular to a solid insulator for an AC metal-enclosed switch cabinet. The wall tube insulator comprises an annular sleeve (1); a projecting structure (3) is arranged along the periphery of the middle section of the inner wall of the annular sleeve (1); a groove is arranged along the periphery of the projecting structure (3); a rubber support pad (2) is arranged in the groove; and the rubber support pad (2) is provided with an opening (4). The wall tube insulator can prevent main bus bars from being scratched or collided and greatly facilitate the on-site installation of main bus bars.