The aim of this work was to identify the pore structure and permeability of clay under various triaxial loading. Triaxial tests were conducted on saturated kaolin specimens, and mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were subsequently adopted to analyze the local pore properties. An improved permeability model was proposed and then used to predict the permeability of kaolin based on MIP results. The influences of the over consolidation ratio (OCR) and the stress path on pore structures and permeabilities were observed. The proposed model is approved to be capable of predicting the permeability of clay with some desirable advantages.