The invention relates to a device and a method for measuring the unique real viscosity of generalized Newtonian fluid. The method includes the following steps of: calculating the real viscosity of polymer melt; calculating the tensile rate on the spindle axis of a pressure sensor in a contracted flow channel; calculating shearing rate; and calculating shearing stress. The device for measuring theunique real viscosity of generalized Newtonian fluid consists of a nose, a visualized charging barrel, a piston screw, a servo motor and a position sensed system. An internal flow channel of the nosetakes contracted shape of continuous gradual change. The piston screw is provided with an axial guide slot structure. The polymer solution or melt passes through a charging device to enter the visualized charging barrel. Under the drive of the servo motor, the piston screw presses down materials to be squeezed out from the nose at a constant velocity. Pressure signals in flow process are collectedand enter a computer data system to calculate the real viscosity. The device and method can not only reflect the shearing viscosity of materials, but also reflect the elongational viscosity of materials, and effectively solve the uniformity problem of the elongational viscosity and the shearing viscosity.