Abstract: The paper proposes a compact two-port dual band-notched ultra-wideband MIMO antenna. The proposed antenna consists of two circular monopole antennas and a defected ground structure, meanwhile, the two open circular ring slots are etched on the radiators and terminal short-circuit low-high-low stepped impedance resonators are etched next to the two 50Ωfeeding micro-strip lines, which achieves dual band-notched function and inhibits the interferences of WLAN(5. 15~5. 85 GHz)and WiMAX(3. 4 ~3. 8 GHz)to the system. Isolated stubs are etched on the top and bottom layers of the sub-strate to improve the isolation. The experimental results show that the proposed antenna has a working impedance bandwidth from 3. 0 to 13. 8 GHz at -10dB, and the first notched band happens from 3. 37 to 3. 85 GHz and the second notched band happens from 5. 02 to 6. 14 GHz, which inhibits the signals of WiMAX and WLAN. Besides, the proposed antenna has the minimum isolation (13. 5 dB), the maximum gain (4. 94 dB) and the maximum efficiency (96. 6%) in the operating frequency band, and the envelope correlation coefficient (ECC) is less than 0. 07, which shows that the proposed antenna is suitable to be applied in MIMO system. Also, the proposed antenna has a compact structure with the overall dimensions of 47. 5 mm×47. 5 mm×0. 8 mm, which is a good candidate for portable devices.