The invention discloses a hole forming machine used for diesel engine accessories. The hole forming machine comprises a bottom plate. A through hole is formed in the middle portion of the lower surface of the bottom plate. Lifting columns are fixedly installed on the upper surface of the bottom plate. A bearing plate is fixedly installed on the tops of the lifting columns. A drive motor is fixedly installed at the position, corresponding to the through hole, of the lower surface of the bearing plate. A rotating shaft of the drive motor is fixedly connected with a brake box below the drive motor. The brake box is connected with an annular slide rail in a sliding manner through a slide ring connected to the surface of the brake box in a sleeving manner. The outer wall of the annular slide rail is fixedly connected with the surfaces of the lifting columns. According to the hole forming machine used for the diesel engine accessories, through the cooperation of the drive motor, the brake box and a hole forming head, the hole forming effect can be better; and a brake motor is arranged in the brake box so that a driving gear can drive a gear rod and a hole forming piece to expand outwards when rotating, it is avoided that the hole forming head is replaced when holes with different hole diameters are formed, and the work efficiency is improved.