Abstract: The composite umbilical cable is a combination of power cables, control signal lines and other pipelines. It is generally used to provide electric power, control signals and other chemicals for deep-sea equipment. The high cur-rent of power cables inside the umbilical cable may induce voltage on the control signal lines, which may cause elec-tromagnetic interference to the signal or damage the insulation of equipment. In this paper, the interference of power cables with control lines in different relative positions is analyzed, and the shielding effect of shielding layers with dif-ferent materials and thickness is investigated. The purpose is to show the difference of shielding effect between the e-lectric shielding with conductive materials and the magnetic shielding with ferromagnetic materials. The results show that the effect of the magnetic shielding is much greater than that of the electric shielding.