Abstract: In this paper, A novel Microstrip-fed Monopole antenna having a frequency band-notched function for UWBapplications is proposed and studied.The designed antenna uses the polygon structure,and satisfies the VSWR reguirement of lessthan 2 in the frequency band between 3.1GHz and 11.8GHz. And a pair of U-shaped slots are introduced on the radiator and themicrostrip feed-line to achieve frequency notched characteristic at 5.0GHz ~5.9GHz(VSWR>2).