海底光缆故障定位主要采用电场法和磁场法，文章根据传输理论，分别推导了这两种方法下信号在海缆导体中的衰减公式，分析了其衰减特性。数值仿真表明：当故障点与岸端距离达1 000 km时，在某型号海缆中，使用磁场法探测，衰减超过95%；而使用电场法探测，则不到8%，在抗衰减方面，电场法要远远优于磁场法。

Submarine cable faults are located mainly by using the electric field method and the magnetic field method. On the basis of the transmission theory, the formula for signal attenuation in the submarine cable conductors are deduced when the two methods are used and the signal attenuation features analyzed. Numerical simulation results show that when the fault point is 1 000 km away from the shore end, the attenuation in certain type of cable is over 95% when the magnetic field method is used, but when the electric field method is used, it is less than 8%. That means that in respect of attenuation resistance, the latter is much superior to the former.