The invention discloses a three-phase power autotransformer, which comprises a base, a three-phase autotransformer, a housing, a mounting base and a wind dissipation device, wherein the housing sleeves the upper part of the base; the three-phase autotransformer and the wind dissipation device are arranged in a space formed by the housing and the base; the lower end of the base is fixedly connectedwith a lower cylinder; the lower end of the lower cylinder is fixedly connected with the mounting base; the upper end of the base is connected with a special-shaped slide block through a bolt in a sliding manner; the internal part of the special-shaped slide block is of a hollow structure; an upper cylinder is arranged in the hollow structure and penetrates through the special-shaped slide block;the lower end of the upper cylinder is propped against the upper end of the base; the external part of a reinforcing bushing is fixedly connected with the three-phase autotransformer; a motor is fixedly arranged in a bracket; an output end of the motor is fixedly connected with a lower gear; a lower blade is fixed on the lower gear; the lower gear is meshed with an upper gear; and the upper gearis connected with an upper blade. The three-phase power autotransformer is capable of ensuring that the generated heat is timely transferred and dissipated, is convenient to fixedly install and simultaneously has the effect of preventing dust from being scattered on the upper edge to affect use.