The utility model is a self-locking pulley and relates to technical field of electric power engineering machinery. The main aim of the self-locking pulley is to improve the safety coefficient of work personnel in electric power construction processes. The self-locking pulley is characterized by comprising a pulley apparatus and a pedestal used for connecting with an external rope ladder, and the pulley apparatus is arranged on the pedestal; the pulley apparatus comprises a linking arm, a lock bolt and an elastic component; one end of the linking arm is provided with a hook comprising an opening, the other end of the linking arm is connected with the pedestal through a sliding structure, the linking arm can slide relative to the pedestal through the sliding structure and therefore distance can be set; the pedestal is connected with the lock bolt, the pedestal moves relative to the linking arm through the sliding structure when being under the action of external force, the lock bolt is driven to open or close the opening, one end of the elastic component is connected with the linking arm and the other end of the elastic component is connected with the pedestal. The work personnel mainly use the self-locking pulley to climb onto electrified wire cables to work in electric power construction processes.