Abstract: We study the influence of clay minerals on bound water characteristics and mechanical properties of soft soils. We first use X-ray diffractometry(XRD)to define the mineralogical composition of the soft soils. We also analyze the soft soils under thermogravimetric analysis(TG) and micro-commercial thermogravimetric analysis(DTG)with a simultaneous thermal analyzer. Based on the above analyses,we learn TG and DTG curve features of the soft soils in Huizhou,Shantou,Yangjiang,Zhanjiang,and Shenzhen. These analyses contribute to determining bound water content and boundaries. The test results are as follows. The clay mineral content of the soft soils positively correlates with the adsorbed water content of the soft soils,among which montmorillonite content has a greater influence on the water absorption of the soft soils. As the TG and DTG curves of the soft soils relate to clay mineral types and content,weight-loss valleys in DTG carves may indicate clay mineral types in the soft soils. In addition,we find it difficult to define the boundary between strongly bound water and weakly bound water solely based on TG and DTG curves.