Abstract: For the measurement of three dimensional magnetic field components generated by lightning discharging currents, this paper designs lightning electromagnetic pulse (LEMP) three dimensional magnetic field measurement system, gives timedomain calibration, waveform and data correction, also processes statistics and analyzes natural lightning measurement. intraclood lightning can be distinguished from cloudtoground lightning by peak value of measured field. The striking point and distance between the discharging channel can be determined by megnetic direction finding(MDF) method and acousticoptic method, then the indirect measurement of lightning currents can be realized. Numerical simulation proves that the results consist with the measured results.