In this paper, the influential factors on focusing amplitude of electromagnetic waves by time reversal mirror in a leaky reverberation chamber have been analyzed. Taguchi's method is combined with the finite difference time domain method to optimize the location of single time reversal mirror in the chamber. The optimization results indicate that higher focusing amplitude of time-reversed electromagnetic waves can be achieved via longer recording time and proper position of time reversal mirror in chamber. In the study of time reversal mirror array, it is shown that the increase of the time reversal mirror elements is contributory to the amplification of time-reversed waves, but the combined efficiency deteriorates.