The present disclosure provides a method for computing a support of an itemset candidate based on graph structure data, a method for determining a frequent itemset using the same, and a method for determining a frequent itemset based on a prefix tree. The method for computing a support of an itemset candidate based on graph structure data comprises: converting data in a database to graph structure data (S101); obtaining an itemset candidate from the database (S102); obtaining a connected component corresponding to the itemset candidate in the graph structure data (S103); determining the number of vertices included in the connected component (S104); and determining the number of vertices as the support of the itemset candidate (S105). The method for computing the support of the itemset candidate based on the graph structure data and the method for determining the frequent itemset using the same provided by the embodiments of the present disclosure may avoid spending too much time in obtaining the support of the itemset candidate by scanning the database, which improves efficiency of the algorithm while ensuring effectiveness of the algorithm.