Abstract: A 3th-order active-RC complex filter is fabricated in 0.18 μm CMOS process for the wireless sensor network Radio-Frequency receiver.The centre frequency of complex filter is 3 M Hz and the-3 dB bandwidth can be programmed to 250 kHz or 500 kHz or 1MHz or 2 MHz.The simulation results show that,the passband gain is about 10 dB,the image rejection ratio is greater than 35 dB,the noise figure is less than 45 dB and the third-order intercept point is greater than 29 dBm,The circuit consumes about 0.9 mA current.Through the certification of the simulation,the performance indexes of this design can meet need of the Wireless Sensor Networks Radio-Frequency receiver.