Abstract: The cold compression tests of the powder sintered steels with the carbon mass fraction of 0%, 0.3%, 0.6%, 0.9%, and 1.2% were carried out on the universal material testing machine. The tested stress?strain data were nonlinearly fitted by the Hollomon equation. The behaviors of flow and densification and the deformation mechanisms of pore and grain were analyzed, combining with the microstructure analysis of the powder sintered steels. The results show that, the cold compression strain hardening behavior of the sintered steels conforms to the Hollomon equation, and the ultimate fracture strain decreases with the increase of the carbon content. In the same strain condition, the strain hardening rate of the sintered steels increases gradually with the increase of carbon content, and the densification effect first increases and then decreases, showing the best when the carbon content is 0.9%. With the increase of strain, the pores of the sintered steels are gradually closed, and the grains change from the equiaxed crystal into the flaky structure. During the flow and densification processes, the densification and densification hardening are dominant under the low strains, while the deformation and the matrix work-hardening are dominant under the high strains.