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　Q-switch　Nd　:　YAG　laser　cavity　between　mirror　and　Q-switch,　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.