An electrical connector assembly (100) for electrically connecting an abutment connector (3) comprises an electrical connector (1) with a plurality of contacts (12) and a support device, the support device includes a support member (2) for positioning the abutment connector (3) being assembled in a horizontal direction and a press member (4) assembled to the support member (2), the support member (2) includes a bottom wall (22) and a top wall (21) opposite to each other, the bottom wall (22) includes a spring portion (221) supports the abutment connector (3) to make it disconnect with the contacts (12), when the press member (4) is inserted into the support member (2), the spring portion (221) moves downwardly to make the abutment connector (3) connect with the contacts (12).