An active bias circuit for a power amplifier and a mobile terminal are disclosed. The circuit includes a proportional to absolute temperature (PTAT) current source circuit, a reference voltage circuit, an isolation voltage stabilizing circuit, and a bias voltage circuit. An input end of the PTAT current source circuit is connected to a voltage source (Vbat), and an output end is connected to the reference voltage circuit. The reference voltage circuit generates a reference voltage that is in proportion to a current and a temperature. The isolation voltage stabilizing circuit isolates the reference voltage circuit from the bias voltage circuit, and supplies a stabilized voltage to the bias voltage circuit by using a negative feedback loop. The bias voltage circuit receives the voltage of the isolation voltage stabilizing circuit, and is also connected to the voltage source (Vbat).