The invention relates to a foundation scheme of a transmission line pole and tower under the karstic feature, in particular to a transmission line pole and tower hollow-square type pile anchor composite foundation suitable for a karst region and a construction method thereof. The center is a pile foundation, an anchor rod foundation mounted on the periphery of the pile foundation and a plate typesteel reinforcement cage located in the middle of the pile foundation and containing a surrounding pile foundation are arranged on the periphery, a hollow-square structure is formed on a section, theplate type steel reinforcement cage is a connecting body of the pile foundation and anchor rods, and meanwhile serves as a bearing platform, through concrete pouring, the pile foundation and the platetype anchor rod foundation are connected to form a whole body, and bearing force is provided for the pile foundation. When the foundation is applied to the fact that on the transmission line karst region, in the pile foundation excavating process, during meeting a substrate large karst cave, the pile foundation and the plate type anchor rod composite foundation can be organically combined, comprehensive up-pull / down-press bearing force is improved, the side effect of the karst geology on transmission line building can be effectively solved, it is ensured that the foundation stress meets the bearing force needs, a karst cave does not need to be avoided, the construction period is ensured, and the construction investment is reduced.