Abstract: The Qaidam Basin is located in the northern part of Qinghai-Tibet Plateau where the Cenozoic tectonic activity is most intense in the whole world. The evolution and reformation of the basin is obviously controlled by the dynamic environment formed by the plateau, and it is a "strongly reformed" basin. Based on the special attributes and dynamic environment of the basin, this study reveals the hydrocarbon occurrence conditions and main controlling factors of the basin. It is one of the main reasons for no important breakthroughs in oil and gas exploration of the Qaidam Basin in the early 30 years that the researchers have not gained a deep understanding of the basin attributes. The abundance and distribution of oil and gas resources in the reformed basin are directly controlled by the hydrocarbon-rich depression (or sag) and the retained source rocks after reformation in the original basin, namely "source-controlling of original basin". A comprehensive study on the restoration of Paleogene original basin reveals that the current southwestern part of Qaidam Basin was once located in the hydrocarbon-rich depression area in the hinterland of the Paleogene basin, and the main source rocks are well preserved; there is a giant hydrocarbon enrichment area of more than 3×10⁴km² around Yingxiongling area, i.e., a key oil exploration area. Due to the strong reformation, the Qaidam Basin has been evolved from a relatively simple hydrocarbon-rich depression structure in the Paleogene to a complex structure including such tectonic units as uplift, sag, fault terrace, and slope. The process and results of the reformation directly control the characteristics, distribution, accumulation pattern and resource scale of oil and gas reservoirs or fields, i.e., reform-controlling reservoir for short. The strong reformation of the basin occurred late and the confining pressure in the deep underground was strong. These distinctive reformation characteristics have more advantages than disadvantages for the generation, migration, accumulation and dissipation of oil and gas. Currently, under the guidance of innovative theories, remarkable results have been achieved in oil and gas exploration, and five types of 100-million-ton-level great oil fields have been discovered successively. The determination of the hydrocarbon enrichment areas in the reformed basin has established the intrinsic connection and prediction basis between the discovered and undiscovered oil and gas reservoirs in the study area, and has opened up a broad exploration field for the continuous discovery of multiple oil and gas fields.