Abstract: Dongguan fault basin located in the east of Guangzhou, the bedrock belong to Tertiary system fragmentary rocks, it's alluvial and pluvial sediment. The rock and its weathering grade are different from here to there within basin, because of the different rock-combinations. So the development of soft-interlayer is all-pervading. In a word the rock and soil conditions are extremely complicated and bring adverse affection to engineering construction. This paper summary the characteristics of Tertiary system, according to geotechnical investigation during the past years in the basin. Our work can provide important reference for the engineering constructions in those areas.