Abstract: An hydraulic brake system that rapidly and precisely slows or reduces speed by constraining or stopping the movement of a link mechanism connected between a piston and a rotational driving shaft of a power system with physical force generated due to the incompressible fluid characteristic by constraining or stopping the flow of oil filled in an hydraulic oil chamber. The hydraulic brake system includes a lubricating section for supplying the oil reserved in a protective casing to friction sliding parts of respective components through pumping movement by utilizing the reciprocal movement of a piston rod, and an oil supplement section for supplementing the hydraulic oil chamber with the oil. Accordingly, the possible abrasion of the respective friction sliding parts is constrained, and the durability is improved. Further, in the event of an oil leakage, the oil is supplemented for emergency-braking, so that a possible accident can be prevented.