The Gymnarchus Niioticus fish(GNF)cruises generally with high efficiency with long dorsal-fin torsional wave propulsion while keeping its body for the straight line.It provides references for bionic propulsor design.According to kinematic observations,the swing amplitude of GNF fins is usually in the 60° to 90°,and in normal state of tour,its amplitude is close to 90°,only in the control of hovering or swimming at very low speed,its amplitude is smaller(about 60°).