The radiation effect of the electrical fast transient (EFT) is usually more serious than that of the conduction and more difficult to be suppressed in electromagnetic compatibility (EMC) test.The energy of EFT concentrate at the range below 100MHz, which means the disturbance in circuits is mostly caused by the radiated energy of EFT through cable coupling.This paper established a calculation model about double parallel cables and did a lot of numerical calculations about EFT coupling between the cables using the theory of transmission line.The characteristics of cable coupling of EFT under different exciting voltage, cable spacing, cable height and load impedance were researched systematically.An experimental device of cable coupling of EFT was designed for verifying the calculation results, which provided an important guidance for EFT suppression and system wiring.