The distribution characteristics of soft clay in Nansha, Guangzhou were examined based on the data of 4 280 boreholes with high density and uniform distribution in association with the coastal history of Guangzhou and ¹⁴C test results. According to the genetic age and sedimentary characteristics, the soft clay in Nansha was divided into two layers. The upper layer was formed in Holocene, whose ¹⁴C age was 1 500-8 500 years, and the lower layer was formed in Pleistocene, whose ¹⁴C age was 34 000-42 000 years. The engineering properties of the two layers were systematically compared via statistical analysis on the physical and mechanical parameters. The research results unveiled that the soft clay in Nansha covers an area of 718 square kilometers, accounting for 91.6% of its total area, with an average thickness of 15-20 m. In general, the soft clay in Nansha is of high water content, large void ratio, low shear strength, strong compressibility and weak permeability. Compared with the lower layer, the upper soft clay has higher thickness, void ratio, pore ratio and compression coefficient, lower shear strength and less fine sand content.