Abstract: By analyzing theoretically the electrostatic field change of a CG lightning leader process, it is indicated that temporal variation rate of electrostatic field dE/dt caused by leader development is better than net field change △E for characterizing the leader propagation. Starting position of the leader, velocity of leader propagation near the ground and leader instant current when leader reached the ground could be determined by using the time-varying curve of dE/dt. Meawhile, the features of inclination or flexion of lightning channel can be infered from the distribution of extreme value point by the curve of dE/dt versus time.