Abstract: Tectonic migration is important both in theory and practice in the course of researching for the formative features and evolving patterns of oil and gas basins, as well as for predicting the types of oil and gas pools, selecting favourable areas, estimating reserves, therefore, directing exploration, and finding the time-space distributive patterns of petroleum. On the basis of the data of geology, geophysics, drilling and satellite image, the evolution process, formative features, tectonic types and distributive patterns for Alashan arc Basins are discussed. The top of the arc is located around Minqin County. The splitting and falldown of blocks in the basins and their subsidence and depositing centers were migrated from the top to the wings of the arc through the whole time. Finally, the conditions of petroleum geology of the basin system are discussed in the paper, pointing out that the areas around the top of the arc and Basins adjacent to it are most prospecting.