For the research of constitutive relationship and parameters of expansive rock, two typical expansive rocks, namely marl and clay rock, Xinxiang section of the Mid  route of South-to-North Water Transfer Project are selected to perform the triaxial consolidation-drainage tests. Through the non-linear elastic models of Duncan, namely the E- μ and E-B models, the parameters calculation and curve matching comparison are conducted for the constitutive relationship of expansive rock, and the relative merits and suitability of different constitutive models are evaluated in the research of the constitutive relationship of expansive rock. Meanwhile, the recommendatory value of constitutive parameters is also proposed for the expansive rock of Xinxiang, and a basic reference is provided for the design and construction of canal slope of similar projects in expansive rocks of this district.