Focusing on the disadvantages of traditional PLC in DCS, a switch signal card based on CANopen bus is designed, which is used to control switch signal in the process of industry production. It gives the design principle of the hardware and software of the board card. On the basis of researching device profile DS401, it emphasizes on the communication mechanism of PDO which is most common communication object in CANopen and the process of input/output of switch signal. In addition, using probabilistic method to deal with jetters of switch signal acquisition. Finally, functional test and analysis is conducted and results show that the card is reliable on data transmission, and has a positive impact on the promotion of CANopen.