A method for monitoring a network device, wherein the method is applied to a network management system, and the method comprises: acquiring basic service set identifier BSSIDs of wireless network devices in a network system managed by the network management system; determining BSSIDs of unauthorized wireless network devices in the acquired BSSIDs of the wireless network devices in the network system by using a fingerprint database of authorized wireless network devices, wherein the fingerprint database of the authorized wireless network devices comprises all BSSIDs of the authorized wireless network devices, and the fingerprint database of the authorized wireless network devices does not comprise the BSSIDs of the unauthorized wireless network devices; acquiring a media access control MAC forwarding table corresponding to a network port used by a user, wherein the MAC forwarding table comprises a MAC address of a wireless network device connected to the network port; and determining, according to the BSSIDs of the unauthorized wireless network devices and the MAC address, an unauthorized wireless network device connected to the network port; wherein the determining, according to the BSSIDs of the unauthorized wireless network devices and the MAC address, an unauthorized wireless network device connected to the network port comprises: processing the BSSIDs of the unauthorized wireless network devices according to a longest match principle and by using a bit mask, and processing the MAC address according to a longest match principle and by using the bit mask, and obtaining processing results corresponding to the BSSIDs of the unauthorized wireless network devices and a processing result corresponding to the MAC address, wherein a minimum number of bits of the bit mask is set for a match; detecting whether the processing results corresponding to the BSSIDs of the unauthorized wireless network devices are the same as the processing result corresponding to the MAC address; and if a processing result corresponding to a BSSID of the unauthorized wireless network device is the same as the processing result corresponding to the MAC address, determining, according to the MAC address, the unauthorized wireless network device connected to the network port. acquiring basic service set identifier BSSIDs of wireless network devices in a network system managed by the network management system; determining BSSIDs of unauthorized wireless network devices in the acquired BSSIDs of the wireless network devices in the network system by using a fingerprint database of authorized wireless network devices, wherein the fingerprint database of the authorized wireless network devices comprises all BSSIDs of the authorized wireless network devices, and the fingerprint database of the authorized wireless network devices does not comprise the BSSIDs of the unauthorized wireless network devices; acquiring a media access control MAC forwarding table corresponding to a network port used by a user, wherein the MAC forwarding table comprises a MAC address of a wireless network device connected to the network port; and determining, according to the BSSIDs of the unauthorized wireless network devices and the MAC address, an unauthorized wireless network device connected to the network port; wherein the determining, according to the BSSIDs of the unauthorized wireless network devices and the MAC address, an unauthorized wireless network device connected to the network port comprises: processing the BSSIDs of the unauthorized wireless network devices according to a longest match principle and by using a bit mask, and processing the MAC address according to a longest match principle and by using the bit mask, and obtaining processing results corresponding to the BSSIDs of the unauthorized wireless network devices and a processing result corresponding to the MAC address, wherein a minimum number of bits of the bit mask is set for a match; detecting whether the processing results corresponding to the BSSIDs of the unauthorized wireless network devices are the same as the processing result corresponding to the MAC address; and if a processing result corresponding to a BSSID of the unauthorized wireless network device is the same as the processing result corresponding to the MAC address, determining, according to the MAC address, the unauthorized wireless network device connected to the network port. processing the BSSIDs of the unauthorized wireless network devices according to a longest match principle and by using a bit mask, and processing the MAC address according to a longest match principle and by using the bit mask, and obtaining processing results corresponding to the BSSIDs of the unauthorized wireless network devices and a processing result corresponding to the MAC address, wherein a minimum number of bits of the bit mask is set for a match; detecting whether the processing results corresponding to the BSSIDs of the unauthorized wireless network devices are the same as the processing result corresponding to the MAC address; and if a processing result corresponding to a BSSID of the unauthorized wireless network device is the same as the processing result corresponding to the MAC address, determining, according to the MAC address, the unauthorized wireless network device connected to the network port.