A 3rd order Bessel complex gm-C filter which uses Nauta’s transconductor for a low-IF receiver of IEEE802.15.4 was discussed．To avoid variance of technology and enviorment effects on cut—off frequency this filter used an on—chip tuning circuit based on PLL．Based on HJTC-0.18 um 1P6M CMOS technology，the filter is centered at +3 MHz and have a passband of 2.6MHz．Simulation results showed that adjacent and alternate channels are attenuated by 26.4 dB and 44 dB．The image signal is rejected by 31.4 dB and the in—band SFDR is 54.8 dB．The complex filter and tuning circuit dissipates 1.61 mA current from a 2.5V supply．