Control units of the kernel module, the fault simulation module and the arcing fault device module used in a physical simulation system of distribution network are designed on the basis of Programmable Controller (PLC) with structured and modular software. The analog circuit breaker on-off control, three-remote data acquisition control, fault simulation control, arcing control are realized by using the designed units. And simulation fault of system can be removed by interruption way and the response time is no more than ten cycles. Results of PSCAD simulation are in accordance with the running experiment results of physical simulation system, which shows that these designed control units can meet the control requirements of the physical simulation system. This work is supported by National Natural Science Foundation of China (No. 51677030) and Natural Science Foundation of Fujian Province (No. 2016J01218).