A connector assembly includes a cable connector and a receptacle connector. The receptacle connector includes a receptacle housing defining a receiving slot and a number of contacts including multiple first contacts and multiple second contacts. The second contacts include a number of differential signal contacts and ground contacts among which the differential signal contacts are paired and the ground contacts are located at opposite lateral sides of each paired differential signal contacts. The first contacts are ordinally arranged as GGVV, or VGVG, or VVGG, or GVGV, or GVVG, or VGGV, or VSSG, or GSSV. The second contacts are compatible to USB 3.0 protocol for high-speed signal transmission. As a result, it is easy to control the impedance of the whole transmission system so as to decrease signal attenuation and signal reflection.