Based on comprehensive reflection on development level and capacity of the commerce and trade circulation industry in west region, this paper constructs comprehensive evaluation indicator system including such four first grade indicators as development basis, contribution, status and growth capability of commerce and trade circulation industry. The sequential overall principal component analysis method is used to measure comprehensive level of commerce and trade development from 2005 to 2010 of twelve provinces and municipality in west region. On the basis of this analysis, the west region is divided into three sectors by cluster analysis and the regional difference is measured and decomposed by Theil index. The result shows that, as a whole, the development level of the commerce and trade circulation industry in west region is relatively low, in addition, the regional difference among the three sectors has relatively big contribution to the difference of commerce and trade circulation industry in west region.