The invention discloses a nodular cast iron pipe outer circle grinding machine. The nodular cast iron pipe outer circle grinding machine comprises a grinding shaft frame and a frame. A drive motor is arranged on the grinding shaft frame through a second hinged shaft base and is connected with an abrasive wheel arranged at one end of the grinding shaft frame. The grinding shaft frame is an L-shaped steel frame. The long side of the grinding shaft frame is connected with the frame through a first hinged shaft base. The first hinged shaft base and the second hinged shaft base are each in a reverse triangular shape. A hinged shaft of the first hinged shaft base is fixed to the frame. The top of the second hinged shaft base is connected with the top of the grinding shaft frame through a bolt pull rod in a threaded mode. The second hinged shaft base and the abrasive wheel are arranged on the two sides of the joint of the grinding shaft frame and the first hinged shaft base respectively. The grinding shaft frame can be directly arranged on the top of the first hinged shaft base, the gravity center of the whole machine is lowered, stability is improved during grinding, the drive motor can participate in balance weight regulation as well, no large-mass balance weights need to be used for the end, close to the drive motor, of the grinding shaft, loads on the grinding shaft frame are reduced, and the fault rate is effectively decreased.