A digital-controlled programmable gain amplifier(PGA) is designed for the RF front-end circuits of large scale wireless sensor network. Five serial stages are employed in the PGA and Each stage is composed of a programmable attenuator followed by a fixed-gain amplifier that has the function of DC-offset rejection. Variable gain is achieved via two steps. The 6dB gain steps are implemented using the R-2R ladder network and the 0.75dB gain step is implemented by a series ladder linear attenuator. Simulation results show that the PGA provide a 78dB gain control range with 0.75dB step and the overall gain accuracy was 0.7mdB. The OIP3 is 16.1dBm. The PGA is fabricated in 0.18μm 1P6M CMOS process and occupies 0.08mm active area.