ABSTRACT In this article the emergence , development and present of depolarizer has been studied by me. Then I havestudied the all quartz depolarizers existed in present. Such as single plate depolarizer , loyt depolarizer , single wedge depolarizer , right angle prism depolarizer , J. C. kremen double wedges depolarizer by theoretical analysisand experiment measurement. I have found when the polarization plane of the incident monochromatic light is un-known or frequently varies , the emergent light can not been depolarized completely by using the all depolarizersexisted in present. According to this situation, I have invented a new type double wedges depolarizer. I can depo-larize the emergent light completely whether the polarization plane of the incident is known or frequently varies by using the new depolarizer. The polarization degree of the emergent light is below 1. 0% , transmission ratio is above 90%.1. INTRODUCTIONSince the time of Huygens there has been considerable attention paid to the study of polarized light Many dif-