In this paper, a kind of reconfigurable monopole antenna with multi-resonance and switchable band-notched function is designed and manufactured whose frequency characteristics can be reconfigured electronically to have a singleband notch function in order to block interfering signals from 5.15 GHz-5.35 GHz HiperLAN, 5 GHz-6 GHz WLAN or 7.25 GHz-7.75 GHz for downlink of X-band satellite communication systems. The proposed antenna consists of a square radiating patch, feed-line, and a ground plane with a Fork-shaped conductor-backed plane. By adding an inverted T-shaped and a pair of Lshaped parasitic structures in the ground plane, additional resonances are excited and hence much wider impedance bandwidth can be produced, especially at the higher band, which provides a wide usable fractional bandwidth of more than 135%(3.05 GHz-16.51 GHz). In order to generate reconfigurable band-stop performance, we use a pair of PIN diodes within the antenna configuration. By changing the ON/OFF conditions of the PIN diodes, the antenna can be used to generate a single notch band to isolate and block any interference in the UWB frequency range. The proposed antenna has a small dimension of 12× 18× 1.6 mm3.