In this paper, a miniature circular disc monopole UWB antenna implemented on a FR-4 substrate was proposed. The proposed antenna uses a novel designed microstrip feed line and an improved ground shape. The size of total antenna is about 40 x 30 mm(2), and the radius of radiation element is 6 mm. Both the radiation element and the whole antenna are much smaller than the conventional antenna with a uniform feed line and a square ground. The simulated and measured results show that a good impedance matching over UWB band (3.1-10.6GHz) was realized. An omnidirectional radiation pattern and gain characteristics of the proposed antenna are given.