The Okinawa Trough which lies at the southeast margin of the East China Sea is an active back-arc rift and is a part of the Ryukyu T-A-BA system. Many geological and geophysical studies reveal that the Okinawa Trough has extremely high heat flow, very strong submarine hydrothermal activity, very frequent earthquake, very strong volcanic erption,central graben and well developed active fault, thin crust, and thin lithosphere. Up to now, most investigations have been carried out in the Middle and South Okinawa Trough, very few in the North. Most Scientists think the activity is strong in the Middle and South,but weak in the North. The authors'structural and tectonic analyses of the North Okinawa Trough, based on a great deal of geological and geophysical data, yielded some conclusions as follows: