A mobile terminal device includes a detector, a transceiver, an analyzer, an execution module, and a connection module. The detector generates a probing request signal. The transceiver receives signals sent from a plurality of access points (AP). The analyzer retrieves a plurality of Received signal strength Indications (RSSI) of the plurality of APs and workload of the plurality of APs by analyzing the signals. The execution module generates a plurality of indices of the plurality of APs based on an analysis results, and selects one of the plurality of indices as a best comprehensive index. The connection module establishes a connection between an AP corresponding to the best comprehensive index and the mobile terminal device.