The utility model discloses a segmented alternating-current withstand voltage test device for a 750kV insulating tool, and the device comprises nine lifting supports, fourteen clamping board electrodes, three grounding apparatuses, and a cylindrical electrode. The nine lifting supports are arranged on the ground in a manner of a 3*3 matrix. The fourteen clamping board electrodes are fixedly disposed at the tops of the nine lifting supports, and each lifting support comprises a pedestal and an insulating supporting rod which is disposed on the pedestal and has an adjustable height, wherein the upper end of the insulating supporting rod is provided with a supporting plate. The front three lifting supports in a front lateral row are respectively provided with one grounding apparatus, wherein one end of the grounding apparatus is connected with the corresponding supporting plate and the other end of the grounding apparatus is connected with the pedestal, on which the supporting plate is located, of the lifting apparatus. Two ends of the cylindrical electrode are respectively provided with a high-voltage voltage-dividing lead. The length of each clamping board electrode in the front and rear lateral rows is 2.4 m. The device provided by the utility model achieves that a to-be-tested insulating tool is uniformly divided into 1.2m segments for segmented testing while meeting the requirements of a full-voltage 4.7m testing length under the condition that a 500kV test transformer is disposed.