Physical mechanisms and influencing factors on the effective stress coeffcient for rock/soil-like porous materials are investigated,based on which equivalent connectivity index is proposed.The equivalent connectivity index,relying on the meso-scale structure of porous ma-terial and the property of liquid,denotes the connectivity of pores in Representative Element Area(REA).If the conductivity of the porous material is anisotropic,the equivalent connec-tivity index is a second order tensor.Based on the basic theories of continuous mechanics and tensor analysis,relationship between area porosity and volumetric porosity of porous materials is deduced.Then a generalized expression,describing the relation between effective stress coeff-cient tensor and equivalent connectivity tensor of pores,is proposed,and the expression can be applied to isotropic media and also to anisotropic materials.Furthermore,evolution of porosity and equivalent connectivity index of the pore are studied in the strain space,and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming.Two applications show that the results obtained by the method in this paper perfectly agree with the test data.This paper provides an important theoretical support to the coupled hydro-mechanical research. Physical mechanisms and influencing factors on the effective stress coeffcient for rock / soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous mater and the property of liquid, said the connectivity of pores in Representative Element Area (REA) .If the conductivity of the porous material is anisotropic, the equivalent connec- tivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Chen a generalized expression, describing the relation between effective stress coeff-cient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Future and evolution of porosity and equivalent connectivity index of the pore are studied in the stra in space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.