In gear machining process, in order to facilitate operator to understand the machine operating conditions in real time, gear machining monitoring system was studied. The overall framework of the gear machining CNC system monitoring module was analyzed. The system was divided into three modules. In the gear processing graphical monitoring module, the track simulation and following error monitoring were analyzed and realized. In the alarm monitoring module, alarm information monitoring design, implementation and selfdiagnostic were analyzed and achieved. In machine condition monitoring module, its implementation process was analyzed in detail.