An ultra-wideband (UWB) multi-input multi-output (MIMO) slot antenna with high isolation was designed in this paper in order to meet the requirements of ultra-wideband transmission for high rate wireless communication. It was fed by coplane waveguide (CPW) and printed on FR4 dielectric substrate with a relative permittivity of 4.4. By cutting the corners to the antenna floor, the good impedance matching has been realized. The measured impedance bandwidth of the antenna is from 2.88 GHz to 11.18 GHz, and the fractional bandwidth reaches 118.1%. In order to reduce the coupling degree, the neutralization line structure is used between the two radiating elements of the antenna, which realizes the high isolation of the antenna. The experimental results show that in the working frequency band, the port isolation degree of the antenna is more than 20 dB. The envelope correlation coefficient (ECC) is less than 0.002 and the diversity gain (DG) is greater than 9.996 dB. The antenna has good diversity performance and is suitable for UWB wireless communication systems.