Abstract: Soil mechanical properties change during the consolidation progress, which is related to the changes for pores of saturated clays. Therefore, a thorough investigation of pore evolution characteristics during the process of saturated clay consolidation has important significance for understanding and applying saturated clay drainage in construction. The pore evolution characteristics of the Daya Bay soil are investigated. In order to decrease the void ratio efficiently, saturated fine-grained soil under the pressure gradient is tested. Firstly, cylindrical soil samples are dried by a cryogenic chamber. Secondly, Synchrotron Radiation CT is used to scan the dried samples to obtain high-precision slices. Then three-dimensional models are restructured with Avizo software using grayscale threshold method. Furthermore, porous structures are quantitatively estimated with several of morphological algorithms. Studies show that pores, under the weight settlement, more than 90% are located in 4~10μm and only a few are larger than 40μm. Soil samples, under the pressure of 100kPa and with large pore content will decrease rapidly while its small pores will increase rapidly, demonstrating that pores are more sensitive to pressure under the initial state. Medium and large pores can be split into small micropores or easily eliminated after being compressed. The results show that aperture with increasing pressure changes gently, small pores and micro pores have more advantages. It can be conclude that small and micro pores have stronger anti-pressure ability. After the pressure gradient, the original flocculation structure gradually changes to the flat stacked structure, particles repel parallels, porosity abundance decreases gradually and pores become elongated in a level direction. In this study, a three-dimensional model with real pore structure characteristics is established using the combination of CT scanning and Avizo(an advanced 3D visualization software).It analyzes the consolidation mechanism of the saturated fine-grained soil from the microscopic perspective.