The present invention relates to a piston valve assembly which is used in a continuous damping control damper using magneto-rheological fluid. The piston valve assembly is coupled with an end of the piston rod, and a stopper having a flat upper surface which is surface-contacted with an upper plate is disposed between a core assembly and the upper plate, thereby properly dispersing a force applied to the piston rod.According to the present invention, the reliability and stability in the coupling between the piston rod and the piston valve assembly can be increased, thereby stably controlling the damping force of the damper. Further, the slot is formed in the core of the piston valve assembly so as to reduce the damping force in the lower speed range, thereby considerably improving the driving comport of a vehicle.