1. A stop word identification method, wherein the method is executed by an information retrieval system running on a computing device and comprises: receiving a first query comprising a plurality of words; acquiring a session identifier (ID) corresponding to the first query; acquiring, according to the session ID, a second query that belongs to a same session as the first query; determining that the first query and the second query forms a query chain, wherein the second query meets at least one of the following conditions to form the query chain with the first query: a length of a longest common clause of the first query and the second query is greater than a first threshold; or a minimum quantity of operations required for converting the first query into the second query is less than a second threshold; or the first query is mapped to a first vector, the second query is mapped to a second vector, and an included angle or a distance between the first vector and the second vector is less than a third threshold; and based on the determination: acquiring a change-based feature of each word in the first query relative to the second query; and identifying a stop word in the first query according to the change-based feature of said each word in the first query relative to the second query.