The paper mainly analyzes and studies mode of bus communication based on optical fiber at one_point to multiple_point and mode of point_to_point communication based on wireless at one_point to multiple_point. The advantages and disadvantages of two communication modes are given. Considering the demands on FA data communication,the paper presents transmitting data based on network mode and connection mode,implementing application protocol based on object oriented mode and international standard. Considering the requirements of FTU unit for data communication, the paper proposes the network inner operating system in FTU unit, which is indispensable. Data are transmitted on client/server mode, defined and organized on object oriented mode and transmitted on logical address.