Disclosed is a broadband 5G MIMO mobile phone antenna based on an orthogonal mode pair. The antenna comprises a metal floor, a metal frame, and one or more orthogonal antenna pairs, wherein one or more floor gaps are formed in the long edge of the metal floor; the four sides of the metal frame are closed, and an even number of frame gaps are formed in the metal frame; and each group of orthogonalantenna pairs comprises two antenna units, wherein the antenna unit comprises a central feeding branch, a first side feeding branch, a second side feeding branch, a first coupling branch and a secondcoupling branch. The two antenna units in the orthogonal antenna pair are in an orthogonal mode, so that high isolation characteristics can be realized under the integration of double antennas. In addition, the metal frame and the multi-mode cooperative work and the like are adopted for further broadening the bandwidth of the antenna units. The antenna has the advantages of being wide in broadband, compatible with the metal frame, high in isolation degree, small in clearance, integrated in a double-antenna mode and the like, and is suitable for the 5G MIMO antenna of various small mobile terminals with mobile phones as representatives.