The invention discloses a line protection method and device. The method includes a step of connecting a secondary winding of a current transformer to a suspended operational line side busbar differential protection when a current line is in a first operating state, and a step of disconnecting the secondary winding of the current transformer from the busbar differential protection when the currentline is in a second operating state. According to the line protection method and device, the technical problem of increasing equipment investment due to the configuration of a short lead protection device during initial construction is solved.