Abstract: The dimensional variation is one of the factors impacting assembly performance.Dimension chain model used to analyze complex relations among dimension chains is built to control dimensional variation.This paper analyzes the multiple levels and hierarchies during auto-body assembly.Reference Point System and functional dimension system are used to establish a multi-hierarchy dimension chain model.The dimension chain consists of automobile level,assembly level,sub-assembly and part level dimension chains.The numerical example shows that the multi-hierarchy dimension chain model can decompose and optimize the complex dimension relationship in the auto-body assembly.Therefore,the complicated auto-body dimension analysis and the variation design can be organized and managed with the model.The model can provide an efficient approach for improvement of auto-body design and production.