An electrical connector assembly, including: an insulating body, concavely provided backward with an insertion cavity at its front end; multiple terminals, each having an elastic contact portion extending into the insertion cavity; a metal shell wrapping the insulating body; a shielding sheet, provided with an elastic piece protruding and extending into the insertion cavity; and a dustproof base, having a tongue and two guide walls located on two sides of the tongue. The guide walls fit with outer wall surfaces of the metal shell to fix and guide the tongue to be horizontally inserted into the insertion cavity. At least one of the elastic piece and the elastic contact portion elastically abuts the tongue to further fix the dustproof base, thus easily fixing the dustproof base.