This paper proposed a novalutralwideband (UWB) bandpass filter (BPF) based on miscrostrip multimode resonator. The filter consists of a miscrostripstubloaded threemode resonator and a pair of novel dumbbellshaped defectedground structure for harmonic suppression. In addition, the stub of the threemode resonator is modified into a stepimpedance stub to achieve the desired band width. A crossfinger feeding structure with a backgroundaperture compensation technique is also used in this filter design to strengthen the energy coupling. The simulatedresults of the proposed UWBBPF show a 3 dB passband with a fractional bandwidth over 81.8% (within 4.04~9.63 GHz), insertion loss lower than 0.2 dB, return loss over 24 dB and 10 dB stopband extending to higher than 30 GHz. The passband of the BPF also shows a very sharp skirt property because of the transmission zeros at both the lower and upper side of the passband. The UWB spectrum mask issued by the Federal Communication Commission(FCC) is satisfied well by the designed BPF. The structure of the proposed UWB BPF is quite compact (smaller than 0.5λg×05λg at the central frequency) and easy to fabricate at low cost because its minimum stripwidth and minimum gapwidth are both 0.1 mm.