A liquid-cooling heat dissipation system capable of regulating water quality includes a first liquid inlet, a first liquid outlet, a heat exchange unit, a sensation unit, a water quality regulating unit for containing and releasing an agent and a control unit. The heat exchange unit has a heat exchanger, a first pump and a mating opening connected with the water quality regulating unit. The sensation unit detects the pH value of a first working liquid and transmits a sensation signal to the control unit. The control unit compares the sensation signal with a preset pH value range to generate and transmit a comparison result to an external interface, whereby the water quality regulating unit is manually controlled to release the agent or not. Alternatively, according to the comparison result, the control unit automatically controls the water quality regulating unit to release the agent or not.