In this paper, the performance of shock ignition with varying ignitor is analyzed theoretically and simulated numerically. First, based on the formation and the collision of shock waves, effects of ignitor pulse on shock ignition are investigated theoretically. Then simulations are performed using a variety of ignitor pulses, determined by their peak powers, pulse widths and rise times, and the ignition window is employed as an evaluation criterion of the shock ignition performance. The obtained results show that the peak power of ignitor pulse is one of the key factors to successfully ignite the core, and the ignitor pulse must be wide enough to provide sufficient ignition energy, however, as the rise time of ignitor is not so long(~ns), it will not degrade the performance of shock ignition significantly.