A locking system for an electronic device housing comprises a top plate, a movable cover pivotal about a first edge of the top plate, and a lateral plate connected to a second edge of the top plate which is perpendicular to the first edge. The top plate defines an opening near the second edge thereof. The locking system comprises a flexible lock-receiving portion, an engaging portion, a groove, and a disengaging member. The flexible lock-receiving portion protrudes from the top plate within the opening and has a protrusion extending downwardly. The engaging portion is formed on a surface of the movable cover and faces the opening. The groove is defined on the lateral plate corresponding to the opening. The disengaging member is inside the groove and protrudes to engage the protrusion.