Abstract: The study of the formation mechanism of aeolian landform hasn't been made new progress in recent years, and at present it is a key aspect on the research, theoretically and practically, of desert science. On the basis of field observation, many scientists in the field in various countries have proposed some hypotheses, but nowaday these hypotheses are still being under exploration and not identified by site-observations, and at the same time, its physical process is lack of clear delineation. By analyzing the physical process of sand movement and wind flow, the writer understood that these two phenomena have auto-accumulation convergence and as soon as sand grains accumulated to a cone-shaped mound, the underlying grains will be covered and become inactive. The following formula can be used to express the activity of sand mound. The activity of sand mound =active sand grain number/inactive sand grain number sand grain number=CA/V-A≈CA/V Where C is a coefficient less than 1, A is sand grain number deposited on the surface area of sand mound, V is sand grain number contained in the volume of sand mound, A^V. Othewise, sand movement will fall down when the grains accumulated. Sand flow upwindward is continually supplemented, the sand mound is heightened gradually and developed into typical aeolian landform. Barch-an dune is exemplified to show genesis and development processes of aeolian landform. Aeolian landform can't be infinitely extended and heightened, as it is limited by wind velocity. More sands will de blown away by the increased wind velocity which occurred along with the heightness of saad accumulation when the relief is climbed to a certain height. Therefore, the relief can't be upgraded more tftie to the countceration between the wind-blown sands and the accumulated sands. The distance between one relief to anothers is controlled by the richness of sand sources.