Based on X-ray diffraction and scanning electron microscopic analyses of Quaternary clayey soil from Kunming basin area, the authors have extensively studied the combination, mineralogy and micro-textures of the clay minerals, and discussed the relationship between the clay minerals and the land subsidence under the overdraft of the groundwater which may alter the combination, micro-textures and physicochemical conditions of the clay minerals. The results show that, under the same condition, the content, mineral combination and micro-textures of the clay minerals play most important roles in leading to land subsidence.