The invention discloses a lens diopter Moire measuring device and a measuring method based on the device. The measuring device comprises a light source, a beam expanding lens, a diopter compensating lens, a first optical grating, a second optical grating, a strip receiving unit, a strip collecting unit and a strip analyzing unit. The measuring method comprises steps of measuring device adjustment, image acquisition and image processing. In the measuring device, a semiconductor laser with a larger divergence angle outputs the light source in a manner of optical coupling, thereby improving quality of optical beams. The measuring device is simple in structure, lower in cost, firmer and simpler to operate and maintain, and requires less on working environment. In the measuring method, the lens diopter compensating mechanism is added in front of a to-be-measured lens, so while the identification precision of Moire strips is ensured, diopter measuring range of the measuring device is extended.