Abstract: Simulations and experiments have been done to find out the suitable circuit parameters, with which the pre-pulse flowing from the Blumlein pulse forming line during the charge cycle can reset the magnetic cores in the double-pulse induction cavity adequately. By the circuit simulations, a new modulus, named “the maximum reset pulse-width”, has been proposed to mark the reset ability of pre-pulse. The veracity of the modulus has been proved by the experiments. By adjusting the load of the Blumlein line according to the requirements of the modulus, the auto-reset problem of cores of the linear induction accelerator cell using “cable delay” double pulse power system can be solved with the least effect on the primary pulses.