Abstract:A kind of electronic device was developed, which could be used to debug, run simulation and fault diagnosis in the host of Huazhong HNC21M3 milling NC system. The hardware circuit principle and embedded programs of the device were designed. The device could simulate machine tool situation through program, could connect with spindle, servo, PLC and other interfaces of NC system host; aiming at NC system host, the parameter debugging, PLC program debugging, simulation operation, fault diagnosis, etc. could be made.