Alpine meadow desertification in Maqu County is a typical case of desertification in the alpine and humid regions of China. The causes, trends, and management of desertification have received considerable attention; however, due to the limitations of research methods and other factors, the precise positioning of sand sources is still unclear. Here, we combined a three-dimensional laser scanner with traditional methods, such as field surveys and indoor analysis, to locate sand sources accurately from a morphological perspective. The results showed that the regional annual sand drift potential was 164.34 VU, synthetic sand transport potential was 91.57 VU, synthetic sand transport direction was 132.37°, and wind direction variability was 0.56, which belonged to a medium-ratio low wind energy environment. According to the complexity of the contribution of regional sand material, this paper further subdivides the sandy zone along the Yellow River into two types: blowout desertification and complex desertification. The blowout desertification was characterized by isolated sand dunes with a slightly smaller area and wind erosion blowout in the upwind direction. The long axis direction was highly consistent with the regional main wind direction, the length ratio of the wind erosion area and sand accumulation area, volume and other morphological parameters, and the special diagnosis of sand material particle size. The desertification process was relatively simple. Also, the sand material mainly came from wind erosion blowout. The complex desertification area was larger than the blowout desertification area. The causes of desertification include dune activation, regional wind erosion, thermal melt slump. The sources of dune material include surrounding activated dunes, wind erosion land, desertified grassland. Compared with the former, the sand source of complex desertification was relatively wide, and the desertification process was complex and diverse. In modern desertification, the wind-eroded depressions around the region were still the main contributors of sand accumulation in the complex desertification type. At the same time, the Yellow River also provides some amount of sand material for regional desertification.