The tunable antenna integrated system may include a tunable antenna module, a bias module, a direct current control module, and a RF module. The tunable antenna module may include a tunable capacitor and an antenna. The tunable capacitor may have the capacitance thereof adjusted according to an adjusting voltage. A resonant frequency of the antenna is controlled by the tunable capacitor. The bias module has a digital/analog converter for receiving a control voltage to generate the adjusting voltage, and the adjusting voltage may be outputted to the tunable capacitor with the value thereof larger than that of the control voltage. The direct current control module is connected to the bias module for outputting the control voltage to the digital/analog converter. The RF module is connected to the bias module, and a RF signal is transmitted between the tunable antenna module and the RF module through the bias module.