The invention relates to an optical fibre communication system and method for a direct-current transmission converter valve monitoring system. The optical fibre communication system comprises a trigger pulse distribution unit, a return signal receiving unit, a first optical splitter, a second optical splitter and a trigger monitoring unit, wherein the trigger pulse distribution unit and the return signal receiving unit are arranged at the side of a valve control system; the first optical splitter and the second optical splitter are arranged at the side of a converter valve assembly; the trigger monitoring unit corresponds to various converter valve sub-modules; the trigger pulse distribution unit transmits control information to the first optical splitter through an optical fibre after multiplexing the control information; the first optical splitter distributes the control information to the trigger monitoring unit corresponding to various converter valve sub-modules; the trigger monitoring unit receives the control information and sending state information; the second optical splitter synthesizes state information of various converter valve sub-modules into one channel and sends the state information to the return signal receiving unit through the optical fibre; and the return signal receiving unit decodes the received state information and sends the state information to the valve control system. Code division multiplexing and time division multiplexing manners are used in the optical fibre communication system for the converter valve; therefore, the connection number of optical fibres between equipment is reduced; and the line cost is reduced.