Extendable and retractable mechanism for connecting plug, and child safety seat

An extendable and retractable mechanism for a connecting plug of a child safety seat, the extendable and retractable mechanism comprising:

• a plug connecting rack arranged slidably back and forth in a sliding direction on a base of the child safety seat, the plug connecting rack comprising a plurality of first adjusting concave portions, and the plurality of first adjusting concave portions being arranged in sequence along the sliding direction of the plug connecting rack;
• and
• a locking pin movably supported to allow the locking pin to be kept in a first locking state in that a first end of the locking pin extends into any one of the plurality of first adjusting concave portions, the first end of the locking pin having a slope facing rearwards in the sliding direction, and a locking slot positioned forward of the slope in the sliding direction;
• wherein, when the locking pin is in the first locking state, the slope is in contact with an edge of the any one of the plurality of first adjusting concave portions and part of a wall of the plug connecting rack located at the any one of the plurality of first adjusting concave portions is locked in the locking slot.