This paper used TSMC SiGe 0.35um technologies to RF power amplifier design for WiMAX 802.16e system application. In the 3.5GHz frequency band average output power 20dBm, gain near 16dBm and joins the linearity construction to raise the overall power amplifier efficiency. Finally design the power detector to transform the power signal, this signal returns gives controls the output voltage for DC-DC IC. This design can improve the power amplifier efficiency. This paper will discuss its design way and the gauging result its characteristic and the future improves the direction.