An antenna device includes a first antenna group comprising multiple antennas, configured to receive and transmitting signals; a second antenna group comprising multiple antennas, configured to receive and transmitting signals; a processor coupled to the first antenna group by a first electronic switch, coupled to the second antenna group by a second electronic switch, configured to divide radiation pattern of antenna combination of the first antenna group and the second antenna group into a predetermined number of characteristic patterns, and further configured to calculate similarities of the characteristic patterns and the RSSI of each characteristic pattern; wherein when the antenna device is in operation, the processor reads and analyzes RSSI of the signals, and compares with the RSSI of the characteristic patterns, and then determines the matched characteristic pattern group according to results of the comparisons and the similarities of the characteristic patterns.