Abstract: In allusion to the field application needs of self-locking devices for T-shaped guide rails applied in the anti-falling protection devices for overhead lines, the mechanical structure and characteristics of the selflocking devices are studied, a guiding and dismantling structure scheme for such a self-locking device is designed followed by simulation calculations and prototype production, which is verified by mechanical tests in labs and application tests carried out at the site of overhead lines. On the basis of ensuring the safety of the self-locking device, it also possesses the function of disassembly, which improves the on-site applicable performance, and solves the difficulties the first-line tower climbers are faced with.