Thin laminar pearlitic colony is the element of a kind of two phase materials,which is composed of the thin lamellas of ferrite and cementite one over the other. With the assumption of small thickness of lamella and small deformation as well as that both phases are elastoplastic, an elastoplastic constitutive description for the pearlitic colony is obtained based on non classical theory of plasticity. The constitutive behavior in different direction and along non proportional path is analyzed. The finite element approach is also used to analyze the influences of the thickness of lamella on the material response. Satisfactory agreement is found between the results obtained by the two methods, which demonstrates the validity of the proposed model.