The invention relates to an intelligent substation optical fiber interface online data mapping transmission method; online data mapping transmission is realized by using an intelligent substation relay protection device; the method is characterized by comprising the following steps: a, all optical fiber interfaces in the relay protection device are configured by using an optical fiber interface configuring assembly, and all data sets, needing to be sent to all the optical fiber interfaces, in the relay protection device are mapped to a backup optical fiber interface; b, all the data sets are copied once by an intelligent device CPU in the relay protection device; c, all the copied data sets are sent to the backup optical fiber interface by using the intelligent device CPU; and d, data are acquired from the backup optical fiber interface by using a receiving device in the relay protection device. The method provided by the invention achieves online data acquisition, testing, control and the like on links without pulling out optical fibers, prevents disorder caused by plugging the optical fibers, has less used time, has high efficiency, and is beneficial for normal operation of power grids.