A new approach using the magnetic field induction is presented to measure transient and steady-state fault currents in non-solidly earthed overhead lines. The paper analyses the characteristics of fault magnetic field around the overhead lines， and the best measurement point for the zero module component of fault current. The zero module current can be measured by inducting the horizontal component of magnetic field. For others off the best point under the overhead lines， the zero module dominated fault current can be measured by the horizontal magnetic field， and the aerial module dominated fault current by the vertical component of magnetic field. The paper proposes to use a cylindrical coil to induct the magnetic field for fault current measurements. Simulation and experimental results demonstrate the feasibility of the method.