The invention provides a distributed system and a method for data interaction between a host and slave units. When one slave unit determines fault occurrence in the system, the slave unit sends a fault recording request to a host through a set GOOSE message; after receiving the fault recording request of the slave unit, the host sends fault recording responses to all slave units through set GOOSEmessages and sends fault recording times to all slave units; all slave units carry out recording on all fault recording times; and after recording, a fault recording message is sent to the host through a TFTP protocol. Therefore, high-efficiency communication of fault data between the slave unit and the host is realized; the efficiency and reliability of fault data communication are improved; thefault ranging accuracy of the transmission line is enhanced; the fault occurrence location on the transmission line is determined; the staff can deal with the fault occurring on the transmission lineconveniently; and thus the normal transmission of the transmission line is ensured.