The invention provides a mobile terminal having a first network module for connecting to a wireless wide area network (WWAN) and a second network module for connecting to a wireless local area network (WLAN). The WWAN and the WLAN connect to a control center. The mobile terminal connects to the WLAN and detects a WWAN signal level of a WWAN signal transmitted by the WWAN and a WLAN signal level of a WLAN signal of a WLAN signal transmitted by the WLAN. The mobile terminal calculates a modified signal level according to a first compensation value and the WLAN signal level and sends the modified signal level and the WWAN signal level to the control center. If the modified signal level is smaller than a first threshold and the WWAN signal level is greater than a second threshold, the control center sends a switch command to the mobile terminal and the mobile terminal switches the connection from the WLAN to the WWAN.