The present invention discloses an optical line transmission protection system and method. In which, the optical line transmission protection system includes: at least one stage of optical line protection segment having a transmitting end provided with a Tunable Optical Divide Module (TOD), and a receiving end provided with an OSW; the transmitting end of a local Optical Line Protector (OLP) is connected to the receiving end of an opposite OLP to form main and standby optical lines; and the TOD is configured to set splitting ratios of the main and standby optical lines according to a difference between the optical fiber states of the current working channel and non-working channel, and tune optical power distributions at respective transmitting ends of the main and standby optical lines, according to the splitting ratios of the main and standby optical lines.