In this paper, based on the basic assumptions of pure bending damage of beams, the elementary equations are drived, in which the definition of bending damage variable is defined by reduction of moment of inertia similar to that of tensile damage variable defined by reduction of loading area, a simple bending damage model is proposed similar to kachanov's tensile damage model. As an example, a bending damage analysis of a beam for creep pure bending is made, the material's constants of the simple bending damage model can be determined in first approximation to kachanov's tensile damage model，the calculating results are compared in good agreement with the results obtained by kachanov's tensile damage model. It shows that the bending damage model is reasonable.