A clutch torque control method for a dual clutch transmission (DCT) vehicle may include a shift initiation determining step of determining whether power-on downshift in which a driver steps on an accelerator pedal to change a current shift stage to a lower shift stage is initiated, and a torque correcting step of correcting basic control torque according to torque-stroke (TS) curve characteristics for controlling a disengagement-side clutch within a real shift range in which a number of rotations of an engine is changed with observer torque calculated by a torque observer when the power-on downshift is initiated, and determining the corrected basic control torque into control torque of the disengagement-side clutch.