Laser has several advantages, such as high brightness, excellent directivity, good monochromatic, good coherence and so on . Therefore, in ranging schemes which combine laser sensor technology and automatic control technology , the laser ranging is most commonly used nowadays . First, we introduce the principle of grating diffraction in this paper, and proposes a method for ranging based on the laser reflection characteristics of target. Let the laser beam reflected from the target through the diffraction grating and lens and image on the CCD. In the horizontal plane perpendicular to the direction of incidence, grating, lens and CCD make up of an imaging device, and which can measure the distance of target for many times by moving itself horizontally. We can calculate the distance through measuring the range between the central point of the CCD and zero diffraction fringe. Then, we analyze the influence from the targets’ scattering characteristics. Lastly, we simulate the different status according to the proportion of mirror reflection of the actual targets’ scattering characteristics and get a conclusion that only the proportion of mirror reflection exceeds a particular ratio can calculate a valid distance.