Abstract: A miniaturized notch ultra-wideband (UWB) filter with novel multimode resonators is proposed in this paper. The new multimode resonator has six resonant modes in UWB band range, which are coupled to the input and output ports through parallel-coupled feed lines. Three of the resonant modes are generated by a sector resonator loaded with a high-impedance short-cut line, while the remaining resonant modes are formed by loading an open-stub on a high-impedance line and etching the circle slot on the fan-shaped low impedance section. Meanwhile, in order to avoid the interference of wireless local area network (WLAN) band and International Telecommunication union (ITU) band on the UWB system, the notch band with center frequency of 5.48 GHz and 8.3 GHz is introduced by loading step open branch on the sector. Finally, an ultra-wideband notch filter is designed, analyzed and fabricated, and the measured results are in good agreement with the simulation results.