The composite wall is the main load-bearing and lateral force-resisting component in cold-formed thin-walled steel structural systems， and the influence of the mechanical behavior of composite walls on the seismic performance of the whole building structure should be paid more attention to. Based on this， a simplified calculation model of cold-formed thin-walled steel composite walls was established. A nonlinear diagonal spring was used to simulate the shear deformation of the composite wall， and a beam-type member was set to simulate the bending deformation of the composite wall. The influence of the door and window holes can be constructed in the model. The calculation method of the axial stiffness of the diagonal spring in the simplified calculation model is derived by referring to the wall equivalent brace method recommended by the Japanese code. Combined with the pseudo-static load test of the composite wall， the correctness of the simplified calculation model of the composite wall is verified. The model meets the design requirements based on elasticity but is not suitable for the elastic-plastic analysis of structures. Finally， based on the simplified calculation model of the composite wall， the finite element model of three-storey cold-formed thin-walled steel structural building was established with reference to the shaking table test specimens. The validity of the simplified calculation model of the composite wall was verified by elastic time-history dynamic analysis， which can provide a reference for the seismic design of light-steel structures.