Abstract: There are several factors influencing the formation of fracture system .In this paper, three scaled analog sandbox models
were constructed to simulate the tectonic evolution of fault in rift basin, to explore the tectonic evolution of Qiongdongnan basin during
the main fracture stage. According to the interpretation of 2D seismic section, the depression in eastern and western Qiongdongnan
Basin shows different tectonic forms. Model results showed that the evolution and development of adjacent depression is affected by the
position and direction of the fault-margin affects, and the basement property had a significant influence on the tectonic evolution. The
formation of graben structure is affected by pre-existing fault, the regional tectonic evolution formed horst without pre-existing fault. The
compound half-graben occur when the basement develop ductile deformation, and the shovel-like half-graben of structural style occur
when the basement develop brittle deformation. Based on the model results, it is proved that the basement property plays an important
role in developing different kinds of fault combination in the eastern and western Qiongdongnan Basin, which provide the paths for
studying the fracture system of hydrocarbon migration and accumulation.

Key words: physical modeling, basement property, geological structural differences, fault combination, sag