Abstract: Weter-ringed transport of oil is an advanced way of shipping oil, especially for viscous oil. The key to the problem is to assure the stability of water ring. Preliminary theorotical analysis and experimnts put light on the reason why water ring is ubstable, and bring about the idea that to keep water ring stable, the core of oil flow must be kept stable structurally so as to prevent oil from sticking to the pipe wall. Technology is presented to keep it stable. At present the industrial conditions are ready for transporting viscous oil in water ring.