Abstract: In order to study the pore structure of foamed concrete and its influence on mechanical properties, the pore structures of three density grades of foamed concrete were tested by X-ray computed tomography (X-CT) technology, and the quantitative characterization of characteristic parameters such as porosity, pore size distribution and pore shape was realized. Based on the grey correlation theory, the correlation degree between different pore structure characteristic parameters and their mechanical properties was analyzed. The results show that the pore size distribution of foamed concrete conforms to the non-standard lognormal distribution, and the pore sphericity has a unimodal distribution, and there is a significant negative correlation between pore volume and pore size. There are obvious differences in the porosity distribution of different densities of foamed concrete in different directions. With the increase of the foamed concrete density, the fractal dimension, median size and median area of pores gradually decrease, and the overall pore sphericity gradually increases. The mechanical properties of foamed concrete are closely related to the pore structure, of which the porosity has the most obvious influence on the strength of foamed concrete, and the grey correlation degree reaches 0.859. The pore size closely related to the strength of foamed concrete is mainly distributed in the range of 100-200 μm, 200-300 μm, and the grey correlation degrees are 0.832 and 0.847 respectively. The closer the pore shape is to spherical shape, the stronger its compressive capacity.