The invention discloses an experimental device and a method for forming fractures and a center circular hole in a disc rock sample. The experimental device comprises a positioning device, a fixing device, adaptors, a cutting piece and a drilling head, wherein the adaptors are mounted on an output shaft of an electric motor of a rock grinder; the cutting piece and the drilling head are mounted on the corresponding adaptors; the positioning device is mounted on an electromagnet of the rock grinder; a positioning column is arranged on the electromagnet; the positioning column is matched with a positioning hole of the positioning device; the fixing device is mounted on a splint of the positioning device through a screw. According to the experimental device disclosed by the invention, damages to the surface of the disc rock sample when the drilling head is drilled out can be avoided, besides, the situation that the axes of two drilling holes are coincident can be guaranteed, and the drilled holes are completely communicated; two edge fractures which are on the same diameter and are symmetrically arranged can be accurately prepared; the situation that a precast center fracture surface passes through the central axis of a disc is guaranteed, and the center fracture surface can be processed according to the designed length of a center fracture. According to the experimental device disclosed by the invention, the processing precision and efficiency of the rock sample can be improved.