According to the requirement and features of fieldbus electric control system (FECS) in power station, an ARM based Profibus-DP V1 slave station is investigated with CSC-831 function of low voltage measurement and control. The typical sub-system of FECS is built and the communication capacity is tested by networking test. The acceptable communication speed for FECS and some applicable problems are discussed as well. Both the main station and the salve station which are designed independently have the lower price and better EMC performance than other special profibus devices.