A novel 4-element UWB MIMO (multiple-input multiple-output) slot antenna with triple band-notched characteristics is designed and fabricated. It is composed of four rectangular slot antennas with two C-slots and a T-slot. To improve the isolation, cross-shaped branches are added. The measured results demonstrate that the antenna can operate ranging 2.51-11.07 GHz with the impedance bandwidth (S11 < -10 dB) of 856 MHz except three rejected bands, including 3.02-4.07 GHz, 4.54-5.83 GHz and 7.88-9.38 GHz, and the inter-element isolation of antenna in the range of UWB band is higher than 21 dB. The presented antenna can filter the interference of WiMAX (3.3-3.7 GHz), WLAN (5.15-5.825 GHz) and X-band (7.9-8.4 GHz). What's more, the parameters of diversity performance like envelope correlation coefficient (ECC), diversity gain (DG), efficiency, gain, channel capacity loss (CCL), mean effective gain (MEG) and total active reflection coefficient (TARC) have been analyzed. Based on the analysis on simulated and measured results, the proposed MIMO antenna is competent for UWB applications with notched bands for WiMAX, WLAN and X-band.