A loop type data transmission system based on a token pass principle, wherein a station whose transmission of data is completed passes therethrough a token to the stations located downstream. The station demanding the transmission acquires the right of transmission when received the token, to perform data transmission with a given station. The token signal is classified into a free token representative of the freedom of the line and a busy token representative of occupation of the line. Among a plurality of stations, only one station is destined to execute detection of transmission failure and remedy thereof. This one station is adapted to convert the free token detected upon reconstitution and repeating of the received information into the busy signal and subsequently re-send the free token. The station having sent out the free token after the completed data transmission is transferred to the state for reconstituting and repeating the received information when the busy token returns to that station.