The invention relates to an auxiliary cable distribution box, in particular to a 10kV outdoor high-voltage cable distribution box and an installation method thereof. An upper part box body of the cable distribution box comprises a ladder-shaped box body, and a left box body and a right box body which are positioned at two shoulder parts of the ladder-shaped box body, wherein the left and right bodies are both in inverted right-angled triangle structures, and are hinged to the middle ladder-shaped box body to form a square box body; the ladder-shaped box body is detachably connected with the lower part box body; and cable connecting accessories are installed in the ladder-shaped box body in a longitudinally arrayed manner. When a cable is installed, the cable connecting accessories and the cable are installed on a rigid support of the lower part box body, and then the upper part box body is assembled with a cover plate. The 10kV outdoor high-voltage cable distribution box has the advantages that the 10kV outdoor high-voltage cable distribution box consists of three detachable movably-connected parts, is convenient to replace, detach and assemble, and is simple, flexible and convenient for construction, external impact is effectively resisted, normal running and working of the cable distribution box are guaranteed, and the technical effect that the inside of the cable distribution box can be operated, overhauled and maintained in an omni-directional manner is unexpectedly achieved.