Chengdu - Mianyang - Leshan (C-M-L for short) high speed railway in Chengdu section is located in the ground of weathered Mud rock overlying deep Chengdu clay area. Based on Chengdu clay ground of in high-speed railway construction project of CML, this article introduced the Burgers model to establish the objective function to analysis rheological constitutive model. The visco-elastic parameters of Burgers model are determined by back analysis of field monitoring data. By the method of iterative back analysis by layer of visco-elastic parameters, based on measured result, predicted the late settlement, and comparison with the follow-up observations records to verify the Burgers model.