A security management system of a home network is provided. The home network includes a home gateway and one or more user devices connected to the home gateway. The security management system further includes a security management server adapted to provide a security management service for the home network. Within the home network, a security management module is disposed to provide a security service for the user devices within the home network. The user devices and a device where the security management module locates have unique device identifications, and the home network has a unique network identification. By the home gateway, the security management server communicates with the security management module. With the network identification and the device identification, the security management server and the security management module achieve a security management for the home network through a registration of the home network and a registration of the user device. A security management method of home network devices is also provided.