A voltage driving apparatus (1) for a power amplifier, a power amplifying system, a power supply device and a communication device are disclosed. The voltage driving apparatus (1) for the power amplifier includes a voltage input module (11), a voltage output module (12), a signal input module (13), and a control module (14). The voltage output module (12) is connected to the power amplifier to provide a voltage. The signal input module (13) is configured to receive a variable input electric signal. The control module (14) is electrically connected to the voltage input module (11), the voltage output module (12), and the signal input module (13) and configured to dynamically adjust the output voltage of the voltage output module (12) according to the variable input electric signal received by the signal input module (13).