Loess origin of Zoigê Basin has been discussed based on synthetic study in grain compositions of the loess, surface texture of quartz sand, as well as other geological phenomena. On the probability cumulative curve of loess, saltation mass and suspension are obvious, and the latter is dominant. Matrix method is adopted to compute grain size of the loess. The statistic analysis on quartz sand surface textures of loess through scanning electron microscope shows the features of air transportation, developed dishing pit, and combined profile features of Aeolian environment.