Abstract: A method having a pruning mechanism to identify wireless APs in multiple-SSID environment that includes the steps outlined below. (A) Wireless signal data in an environment are collected. (B) Only one of the at least two pieces of the wireless signal data having the same BSSID is kept and delete the at least one of the pieces of wireless signal data that has the BSSID derived from a MAC address of wireless APs under management. (C) Only one of the at least two pieces of the remained wireless signal data having the same channel, the same wireless mode, a difference of the RSSI absolute value that is smaller than a first predetermined value and a hamming distance of the BSSID that is smaller than a second predetermined value is kept. (D) Based on a number of the remained wireless signal, a number of the unmanaged wireless APs is determined.