Provided are a gain compensation device and a bias circuit device. A compensation bias current is generated by the gain compensation device to compensate the gain deviation of power amplifier and improve stability of power amplifier. Through high-temperature compensation unit and low-temperature compensation unit in different gears, gain of power amplifier is compensated along with temperature changes, thereby improving feasibility of the gain compensation device. It takes small space, and the circuit only includes the circuits corresponding to high-temperature compensation unit and low-temperature compensation unit, so the circuit is relatively simple and beneficial to miniaturization. In the bias circuit device, based on an initial bias current provided by a bandgap reference, the gain compensation device is added to generate a compensation bias current, and the initial bias current and compensation bias current are superimposed, so that the gain of power amplifier is further compensated, which improves stability of power amplifier.