A novel compact dual-band bandpass filter using tri-section Stepped Impedance Resonators (SIRs) is presented for Wireless Local Area Network (WLAN). SIRs and one stub between parallel couple line are employed to realize two satisfactory passbands. Meanwhile, one transmission zero is generated between the two passbands to achieve a high out-of-band rejection. Simulated results show that two central frequencies are located at desired 2.4 and 5.2GHz with 3dB fractional bandwidths of 6.3% and 3.4% respectively. The measured results are in good agreement with the simulated ones.