In this letter, an ultra broadband antenna (UWB) loaded with defected ground structure (DGS) is presented. The UWB antenna with circle radiation patch is fed with 50Ohm mictostrip line. The DGS structure is introduced to the ground under the feed line and hence the frequency selectivity is also introduced to this UWB antenna. Finally, a compact UWB antenna loaded with DGS is designed, simulated and measured. All the results reveal the effectiveness of the design scheme.