Abstract: Taking Qiongdongnan basin as the research object, on the basis of the seismic data interpretation, we select six typical profiles to conduct balanced restoration. The stretching tensors and stretching ratios of each section in different periods are calculated. On this basis, the structural evolution process and regional differences of Qiongdongnan Basin are analyzed qualitatively and quantitatively. Research results show that: in the middle part of Qiongdongnan Basin, the horizontal extensional rate decreases significantly and is relatively stable, which indicates that the opening of the basin is uniform. Qiongdongnan basin structural evolution can be divided into four stages: during the 65-33.9 Ma:, basin began to extend; during 33.9-23 Ma, tension activity enhanced and activity reached the top; during 23-10.5 Ma: tension activity weakened obviously, and a few inherited faults developed; 10.5 Ma-today: calm deposition with little fault activities. There are obvious differences in structural styles between the east and west parts of Qiongdongnan Basin. In the western part of the basin, there are small number of large displaced faults, which are conducive to the migration and filling of oil and gas from the source rock to the reservoirs, and the formation of a good cap layer in the upper part to prevent the escape of oil and gas. There are many faults in the graben in the eastern part of the basin, with multiple fault stages, complex assemblages and thin sedimentary cap rocks, which are not conducive to the preservation of oil and gas. Basement properties and pre-existing faults affect the structural evolution in the east and west of the Qiongdongnan Basin.

Key words: Qiongdongnan basin, balanced cross section, structural evolution, structural differences, area-constant method