A method of performing WLAN measurement for a communication device in a wireless communication system is disclosed. The method comprises receiving WLAN measurement configuration including a WLAN identity of a WLAN that is to be measured, from a network, scanning WLAN channels to detect the WLAN identity, measuring received power in a channel when the WLAN identity is detected on the WLAN channel, determining if a WLAN access point (AP) can be connected, and transmitting a first message indicating the WLAN is not available to the network after the WLAN identity is not detected or after the WLAN identity is detected but the WLAN access point (AP) cannot be connected.