Abstract: A high power gain RF power amplifier was designed for WLAN 802.11b/g based on 0.13μm SiGe HBT technology.The PA composed of three stage amplifiers worked in Class AB, with temperature compensation and linearing bias circuit.The simulation results showed that the power amplifier had a power gain of 30 dB, an output 1 dB compression point of 24 dBm, the S parameter of S11 less than-17 dB in a wide frequency range from 1.5 GHz to 4 GHz and the S21 more than 30 dB, the output match S22 less than-10 dB and the S12 less than-90 dB, a maximum power added efficiency (PAE) of 42.7% and the efficiency at 1 dB compression point is 37%.