In this paper, the obvious differences of the stress and deformation in the powders and the dense materials, and the rheological behaviors of the powders during the compression process are discussed. The results show that the strain delay, compression creep, stress relaxation of the powders during the compression process are closely related to the compact density, powder characteristics and deformation rate. Based on the stress and deformation characteristics of the powders, the mechanism of the strain delay, compression creep and stress relaxation of the powders are suggested.