Abstract: To realize virtual assembly with tolerance,the product model should be built at first.By analyzing the requirements for product tolerance models in virtual assembly,a concept of hybrid tolerance model is brought forward.The model combines the basal tolerance with the additive tolerance information,links the basic geometry to the precise geometry information,and embraces the abundant engineering semantics information.Detailed are the hierarchy,information source,the mapping method among layers and the expression of geometric precision.At last,the application of the hybrid tolerance model is discussed.