<正> Protein fold structure is more conserved than its amino acid sequence and closely associatedwith biological function,so calculating the similarity of protein structures is a fundamental problem instructural biology and plays a key role in protein fold classification,fold function inference,and proteinstructure prediction.Large progress has been made in recent years in this field and many methods forconsidering structural similarity have been proposed,including methods for protein structure compar-ison,retrieval of protein structures from databases,and ligand binding site comparison.Most of thosemethods can be available on the World Wide Web,but evaluation of all the methods is still a hardproblem.This paper summarizes some popular methods and latest methods for structure similarities,including structure alignment,protein structure retrieval,and Iigand binding site alignment.