Inthispaper,theoperationprincipleoflaserrotaryencodersisexpoundedandtheopticalquadruplefrequencytechnologyusedinlaserrotaryencodersinex-plained,andthedesignideaofopticalsysteminΦ66mmlaserrotaryencoderismainlyintroduced,aswellasthechoiceofprincipaldevices.