A concept of semantic relationship between fuzzy sets is presented in the paper. The concept is not only related to the membership of the fuzzy sets, but also considered releant to the similarity between elements in the domains of the fuzzy sets. So,it can be used to characterize the similarity between fuzzy sets more meticulously than it was done by the various "distance" or "nearness" previously defined in fuzzy mathematics.There fore, it would have a wide range of applications in AI and other areas, such as information retrieval and text classification. Besides, two algorithms to approximately calculate the semantic relationship are given in the paper.