Abstract: The micropore structure and evolution of copper oxide ore particles before and after acid leaching were investigated by high resolution X-ray micro-computed tomography(micro-CT) and three-dimensional(3D) image analysis. The pore structure parameters,such as porosity,pore size distribution,pore connectivity and fractal dimension were statistically calculated. The results indicate that after acid leaching,the porosity increases obviously and the pore size distributes more widely. Some large pores appear and the mean pore diameter increases by 2 to 3 times. There is little pore connectivity before acid leaching,while the pore connectivity increases significantly after acid leaching,being inhomogeneous in three different directions. The fractal dimension of pores also increases after acid leaching,and the porosity and the mean pore diameter grows exponentially with the fractal dimension. 3-D image analysis is a powerful technique to quantitatively characterize the micro-scale pore structure of ore particles during acid leaching,so it facilitates to disclosure the evolution laws of pore structure.