As an important part of the cross-sea transmission system, the bridge-cable has an important impact on the reliability of the entire transmission system. Taking the 220 kV bridge-cable engineering of Zhoudai Bridge as the research object, considering the influence of overhead lines, a simulation model of the bridge cable-overhead hybrid line is established based on PSCAD/EMTDC transient simulation software. The overvoltage characteristics of the cable sheath under lightning strike and operation fault are studied. The results show that when lightning strikes the overhead line, the sheath overvoltage amplitude increases with the decrease of the strike distance, and with the increase of the tower grounding resistance, the maximum overvoltage amplitude can reach up to 46.4 kV, under a single-phase grounding fault, the sheath overvoltage is the most serious when the ground phase angle is 90°, and the maximum overvoltage amplitude can reach up to 15.9 kV, under a non-full-phase operation fault, the cable sheath overvoltage amplitude is not greatly affected by the fault distance. The sheath overvoltage of two-phase disconnection is more serious than that of single-phase disconnection. The research work provides a certain reference for the insulation coordination design of the bridge cable-overhead hybrid line.