In hailaer basin as an example, the paper discusses the types, characteristics, forming conditions and petroleum geological significance of the inversion-phase structures. It is summarized that the characteristics of the three structural types. Non-superimposed newborn extrusion structures, positive inversion structures, and twisting inversion structures, forming in tectonic inversion period of the basin. It also analyzes the forming conditions of the three. The forming conditions of former is the existence of strong extrusion stress field, has not suffered deformation or slight deformation of rock zone in synrift period, and that there are deep and shallow slip planes in the basin. Points out that the inversion-phase structures are the main trap types in extensional basin,that the tectonic inversion period is the mass period of oil and gas migration, which have good matching relationship with inversion-phase structures. Therefore, the traps provided by the tectonic inversion as the most favorable oil and gas gathering place.
