A microstrip-fed ultra-wideband antenna with dual band-rejection characteristics is investigated. The antenna has the same shape between radiation patch and ground plane, and is fabricated on a Rogers RT/duroid 5880 substrate with an overall size of 22×31.85×0.508 mm 3 . To generate two notched frequency bands, a U-shaped parasitic element on the back of the patch is utilized. The two notched bands can be controlled by adjusting the size of the parasitic element. The measured results show that the proposed antenna has an impedance bandwidth of 3.0 to 11.7 GHz for S 11 <−10 dB, expects two eliminated frequency bands 5.08~5.96 GHz for wireless local area network and 8.71~10.25 GHz for X-band.