A receptacle connector includes a main body, an insulating base, a tenon member, a compressing spring, and a cap body. The main body includes a first concave area. The insulating base includes a second concave area. The first and the second concave area constitute a joint cavity and an opening. The tenon member erected on the bottom surface of the first concave area and is threaded through the compression spring. The cap body includes a sheath portion slidably threaded through the tenon member and a cover portion occupied a part of the opening. The sheath portion is connected to the compression spring and when the sheath portion of the cap body compresses the compression spring, the cover portion of the cap body is capable of moving from a closing position to an accessing position relative to the opening.