The paper analyzes the high voltage rectangle pulse generator with a Marx generator and a LC circuit in theory, and designs a pulse generator of this kind. The Marx generator is constituted of sixteen 100 kV, 400 nF capacitors, with a pre-triggered S-type circuit. The LC circuit is made by five capacitors the same as that of the Marx generator and a inductor of 1.5 H inductance. The simulation of Spice shows a 1.1 MV, 300 ns, rectangle pulse produced by this pulse generator. The middle stage of the Marx generator is used to trigger the LC circuit in order to synchronize this two parts.