Immersed tube method is a major construction method for underwater tunnels, of which the key techniques include prefabrication, towing, immersion and connection of tube elements, as well as foundation treatment. The immersed tube tunneling techniques have been so much developed to cross deeper and wider rivers/harbors with complex water flows and difficult ground conditions, as demonstrated by some typical projects such as Maas tunnel in Holland, MRT harbor crossing tunnel in Hong Kong, Tuas cable tunnel in Singapore, Oresund tunnel between Denmark and Sweden, Busan tunnel in Korea and Bosphorus tunnel in Turkey. The technical development in tube element prefabrication, tube element waterproofing, docks and foundation treatment are discussed in this paper.