In order to increase the efficiency of operation and reduce the possibility of misoperation in the substation， the concept of sequence control and the conditions for realizing sequence control are proposed. Three implementing methods of sequence control，that is using the local automation system and dispatch center to realize separately， using sequence control server， and using bay level IEDs together with the sequence control server， are put forward and compared. It is concluded that the method of using bay level IEDs together with sequence control server to realize the sequence control has the advantages of less communication dependency， high executing efficiency， high reliability and maintainability. The relevant functions of sequence control such as graphic operation ticket supervision and verification of graphic operation simulation in the RCS-9700 substation automation system and the implementing procedure of sequence control are described in detail.