A novel reconfigurable lowpass-polyphase biquad filter based on MFB structure is proposed in this paper. In this biquad, only one op-amp is adopted which improves the matching and reduces the power consumption. And its transmission function is synthesized by the complex signal flow graph. Then a 3rd order filter used in Zigbee transceiver is implemented to illustrate the technique, which is realized in 0.13 mu m CMOS technology. To avoid the variation of resistance and capacitance, an on-chip tuning scheme is integrated. The test results show that when in polyphase mode, it is centered at 2 MHz with 3 MHz bandwidth and the image rejection is about 23 dB with the voltage gain of 12 dB. When in lowpass mode, the cut-off frequency is 1.5 MHz, and the DC gain is 12 dB. The in-band 3rd order input intercept point (IIP3) is 9 dBm in polyphase mode and 13 dBm in lowpass mode. Attractively, the filter only consumes 2.3 mA with a 1.2 V power supply, and occupies an area of 0.26 mm(2).