A novel UWB bandnotched antenna was proposed in this paper. The configuration of the antenna was evolved from the conventional circular monopole antenna. The radiator of the antenna was designed to a gradient smileyshaped patch to realize UWB characteristic and a Cshaped slot on the radiation patch was fabricated to realize the bandnotched characteristic. The reasonable selection of the size of the Cshaped slot can effectively remove the interference of WLAN (5.150~5.825 GHz) in the ultrawideband. The simulated results indicated that the bandnotched characteristic (VSWR>2) was obtained within the frequency range of 4.91~6.07 GHz. The proposed antenna structure is novel and simple and suitable for the ultrawideband communication systems.