The utility model discloses a cable connector assembly, which comprises an insulating body and a plurality of conductive terminals accommodated in the insulating body. The insulating body is provided with a butting part and a plurality of accommodating grooves passing through the butting part. Each conductive terminal is provided with a contact part extending into one of the accommodating grooves and used for being in butt joint with a socket connector, and a connection part extending backwards. The cable connector assembly also comprises a flat cable and a built-in circuit board used for connecting the flat cable with the conductive terminals. The built-in circuit board is provided with a plurality of metal connecting pieces welded together with the connection parts of the conductive terminals, and a plurality of metal welding pieces welded together with the flat cable. The metal connecting pieces and the metal welding pieces are electrically connected together. The welding pieces are composed of a plurality of pairs of differential signal bonding pads and grounding bonding pads arranged at the two sides of each pair of differential signal bonding pads. A grounding bonding pad is arranged between every two adjacent pairs of differential signal bonding pads respectively. The flat cable is provided with two grounding wires welded with the same grounding bonding pad.