USB type-C connector and cable was widely used for many systems, covering client systems, IOT and mobile systems. The introduction of USB4 will bring a data rate of 40Gbps to the usage case. integrated S-parameter was implemented to specify the high-speed requirement of USB4 cables and connectors. Special fixtures were developed to evaluate the performance of USB4 cables and connectors. Design considerations of both cables and connectors were explained for SI/RFI performance improvement, including the PCB footprint optimization, contact pin shape design, ground plate design, paddle card design and wire termination design. simulation and test data were used to verify the design optimization. The USB4 cable and connectors were also verified with Thunderbolt 3 system implementation.