Abstract: Programmable logic controller based on PC,with open operation architecture,strong ability of data processing and good network communication,is a new type control technique emerging in current industry automation field,and can meet the demands of open and flexible control system.In order to coordinate with Soft PLC developing system running on PC to carry out corresponding control function,an operating system of Soft PLC is designed and developed.The paper briefly describes the system structure of soft PLC and the function of its operation system,introduces in details hardware structure and development process of its operation system,and provides PCB circuit board.In circuit design,electromagnetism compatibility design is adopted in order that interference between signals as well as from exterior interference source is reduced.The experiment indicates operation system designed can efficiently fulfill communication and control.