Abstract: Experiments have been done to study the magnetic characteristics of the magnetic cores under MHz repetition-rate multi-pulse excitation in the multi-pulse inductive accelerator. With a low-voltage (～1 kV) multi-pulse power system based on the MOSFET solid state switch, the permeabilities of a ferrite core and a amorphous core have been obtain, as well as their magnetization curves under multi-pulse excitation. Significant differences in the experimental results show that the amorphous core is more fit in multi-pulse exciting condition. And in the later experiments on induction cells with ferrite and amorphous cores under high voltage (more than 200 kV) triple-pulse excitation, consistent results have been derived.