Abstract: The design principle,system architecture and key functions of TolRM system are presented. To facilitate the seamless integration of tolerance with CAD systems,a hierarchical structure for tolerance representation is devised.The rule-based methods for evaluating correctness of tolerance ensure that the given tolerance specifications are reasonable,complete and effective.The interpretation method of tolerance semantics is discussed.Variational volumes are used to explicitly illustrate the effect of tolerance.Some techniques are also given to improve the system efficiency.Tested by many samples,TolRM shows good robustness and practicability.