A six-element dual-polarized (DP) endfire multiple-input-multiple-output (MIMO) antenna with high gain is proposed in this article. It is a uniform circular array and placed on a large metal plate (LMP). The edge-folded Vivaldi antenna is employed to provide horizontally polarized (HP) field. The folded halve-Vivaldi antenna is located in the center of two HP antennas (HPA) sharing the radiation aperture, and it can produce a vertically polarized (VP) field. To enhance the gain of each DP antenna element, two different metasurface lenses are integrated on its flare aperture and endfire direction (EFD). It can deflect and focus on the radiated near-field toward the EFD. To demonstrate the design, the proposed DP MIMO antenna is fabricated and measured. For the HPA, it shows an impedance bandwidth of 151.1%, the maximum gain of 15 dBi, the isolation of more than 25 dB, and an envelope correlation coefficient (ECC) of less than −51.3 dB. For the VP antenna, its impedance bandwidth is 151.3%, the maximum gain is 14.9 dBi, the isolation is more than 30 dB, and ECC of less than −56.2 dB is achieved. With these excellent performances, the proposed antenna is used for positioning the electromagnetic interference source (EMIS).