The invention discloses a high-precision experimental device for processing prefabricated three-dimensional single fracture and multi-fracture by using a rock specimen. The high-precision experimental device comprises a body, wherein a fixed block is arranged on the body; a first motor and guide rails are arranged on the fixed block; a mounting block is arranged at the tail ends of the guide rails; a groove is formed in the mounting block; a speed-adjustable handheld electric grinding tool is arranged in the groove and is clamped in the groove by a clamp; a screw is arranged on the speed-adjustable handheld electric grinding tool; one end of the screw is arranged on a mounting plate through a bearing; a slice for processing the specimen is arranged on the screw; the bearing is limited by a bearing end cover; the mounting plate is positioned in a fixed plate; the fixed plate is fixed on a mounting table; the mounting plate vertically moves along the fixed plate. According to the high-precision experimental device disclosed by the invention, the processing depths of the fractures are controlled by driving the slice to move through the guide rails and a gear; by the movement of a moving table, the processing depths of the fractures and the work of a hydraulic rod are controlled, and a processing angle of the specimen is adjusted, so that the processed fractures better accord with the sizes of actual fractures.