The invention discloses a building method for a semantic knowledge base based on a dictionary. The method comprises the following steps that a knowledge database based on a dictionary semantic knowledge expression model is built; semantic knowledge paraphrased by semantic items are extracted according to a semantic knowledge extraction rule; the semantic item mapping for extracting the semantic knowledge is realized; the rest semantic knowledge paraphrased by the semantic items are extracted. The method provided by the invention can be used for flexibly and fast building the knowledge base containing rich semantics from the dictionary, and in addition, the knowledge expressed in the knowledge base has universality and authority. The invention simultaneously provides a deep semantic knowledge expression method and semantic similarity calculation method for semantic information processing of natural languages, wide application values are realized in the natural language processing field such as the information retrieval field, and the retrieval based on the semantics instead of keywords can be realized, so that the deep semantic retrieval result closer to the requirements of the user can be obtained.