By 2020，whether the western region can achieve the goal of building moderately prosperous society is an important issue of concern to the government. Therefore，this paper first introduces the national statistical monitoring index system on building moderately prosperous society and the target value. According to the target value of the index system，this paper studies the realization degree of each index in the western region from 2010 to 2016，predicts the realization degree of each index in the western region in 2020 by the grey forecast model，analyzes the gap between the predicted value and the target value. Finally，the paper puts forward the corresponding countermeasures and suggestions for the large gap index.