A dual-band filter designed for Wireless Local Area Networks(WLAN) is introduced and fabricated. Two-order Stepped Impedance Resonator(SIR) and parallel coupled-line are utilized to design it. Experimental results agree well with simulations, thus validating our design. The insertion losses of two resonant frequencies 2.4 GHz and 5.2 GHz, are 0.85 dB and 1.3 dB respectively. Based on this plane filter, a cylindrical conformal filter is designed through analyzing the influence of conformal cylinder on the resonant characteristic of SIR structure and an accurate modeling method which is consistent with the real fabrication is adopted. The insertion loss is a little bit larger, but the conformal performance and the selectivity become better. This conformal filter can be used in conformal communication system with a broad application prospects.