Two ultra-wideband (UWB) microstrip bandpass fllters (BPFs) are proposed by using tunable E-shaped dual-mode microstrip Stepped-Impedance Resonator (SIR). For the lower band fllter measurement results show there is a passband of 3.1GHz to 5.2GHz and its 3dB fractional bandwidth is 51%. The UWB upper band fllter may be obtained by tuning E-shaped SIR. The measurement results show there is a passband of 6GHz to 10.6GHz and its 3dB fractional bandwidth is 55%. Compared with the similar investigation using the cascade of electromagnetic band gap (EBG)-embedded multiple-mode resonator (MMR) and fork resonator, the proposed approach has some advantages, such as easier adjustment of bandwidths, better passband performances and smaller size etc..