Abstract: In this paper,some problems of hypergraph to which relational schema corresponding are discussed,and the problem of classification is studied.The concepts of quasi-cycle,independent quasi-cycle,basic quasi-cycle,irregular guasi-cycle,regular quasi-cycle,complex quasi-cycle,part re- duplicative quasi-cycle,independent complex quasi-cycle,independent part reduplicative quasi-cycle are proposed.On the basis of this,theory concerned of quasi-cycles such as decomposition and transform of classified cycle is studied.