In order to reveal the relationship between the microstructures and properties of polyurethane foam, an in-situ CT system is built on the 2BM line of APS light source in the US. The deformation and damage of a closed-cell rigid polyurethane foam under quasi-static compression loading is characterized in a three-dimensional (3D), real-time manner, with a resolution of 0.87μm. The stress-strain curve of the rigid polyurethane foam and the evolution of 3D structures in three deformation stages (elastic, platform and densification) are obtained via the in-situ CT test. 3D images show that the local compression bands are observed to propagate from the ends of sample to the center in the platform stage, and the band propagation velocity exceeds the platern velocity. The axial deformation fields of polyurethane foam are calculated accurately using the digital volume image correlation technique, showing that the compression deformation is mainly concentrated in the deformation bands. The deformation process of cells is tracked and the micro deformation of cell walls is quantified with the curvedness index. It is found that the collapse of cells is mainly originated from the folds formed by the buckling of cell walls.