Abstract: The sub-6GHz 5th generation mobile communication (5G) has been commercially utilized, 5G millimeter wave technology is gradually mature and would be commercialized in around 2022. The study on 6th generation mobile communication (6G) has also been started and the publications and reports on the vision and key technologies of 6G begin to increase. This paper will mainly discuss the key role and applications of millimeter wave technologies in 5G and the future 6G.