A compact dual-band bandpass fitter is designed to operate at 2.4/5.2 GHz without any input/output impedance matching. This fitter is constructed of three resonators which are based on the stepped impedance resonators and hairpin resonators. The Al2O3 ceramic with a thickness of 0.6 mm and a relative dielectric constant of 9.4 was adopted as substrate. It is easy to be integrated with other RF circuits by SOP (System on Package) process. The three-order dual-band bandpass filter is optimally designed and its properties are confirmed by experiment. By the high dielectric constant substrate and modified structure, the optimized device exhibits excellent dualband filtering performances and small size. The size of the proposed filter can be reduced about 32.5% in comparing to the typical hairpin filters.