Based on the network communication platform,the islanding protection in the station domain can quickly realize the islanding state judgment which can make up for the deficiency of the principle of active and passive island protection.The current station-domain islanding judgment method which is based on the fixed grid structure analysis does not have universal applicability,so this paper proposes a method based on voltage class topology analysis to judge the isolated island in the station domain,in which the different voltage class characteristics is used to optimize the search path.Compared with the full matrix self multiplication and traditional tree search method,the proposed method is simple,small in memory and fast in computation.It is proved that the method is feasible and applicable to all kinds of grid structures in power system.In addition,this paper also puts forward the error prevention mechanism through the switch position fault tolerance verification to further strengthen the reliability of the protection algorithm.