Abstract: The paper introduced characteristics of Modbus RTU communication protocol, proposed a design scheme of I/O driver for programmable logic control kernel software ProConOS based on Modbus RTU protocol, and conducted on test and analysis. The test and application results show that the scheme can effectively realize interconnection, industrial networking and centralized control of different control equipments which support the Modbus RTU protocol, and provides basis for application of the Modbus RTU protocol in embedded system.