Abstract: The pore wall stress from crystallization of salts or water in rock materials is an important factor to induce weathering and freeze-thaw damage. The pore system of authentic materials is generalized into four kinds of interpenetrating independently ideal shapes as sphere, cylinder, ellipsoid and elliptic-cylinder. Then four types of heterogeneous pore system models are proposed based on the statistical distribution of quantity/volume of pores to their radii. Associated with the crystallization law of heterogeneous pore system, the theory of ideal shape pore crystallization stress and the average algorithm of crystallization stresses, the computing method and formulas for macro-level “average stress” derived from micro-level pore wall stresses of these four models are proposed. Finally, based on the crystallization progress of sodium chloride in heterogeneous spherical pore system, the evolution of macro-level triaxial “average stress” with invasion radius (corresponding to solution concentration of pore system) is discussed.