The transformation course of a quarter-waveplate's rotating polarization plane of elliptically polarized light is deeply analyzed by the Jones vector transformation. According to the principle of A-O interaction and quartz's different characteristic in the direction of parallel and perpendicular acoustics field,with a quarter-wave plate being inserted in an AO Qswitch Nd∶YAG laser cavity between mirror and Qswitch,AO Q-switch's Bragg diffraction efficiency formula is put out theoretically. Consequently,the conclusion has been drawn by calculating simulation that the ability of a single AO Q-switch's switching CW Nd∶YAG laser is increased. Furthermore,the experimental result is well in accord with theoretical analysis.