A hydraulic circuit system for one-touch jack and its structure has an inlet circuit, a return circuit and an overload protection circuit with a hydraulic cylinder, a piston rod, a sequence valve, a safety valve and a relief valve, in which the inlet circuit extends from an outer reservoir of a hydraulic cylinder via a check valve to connect to an oil chamber of a manual pump. The oil chamber of the pump is connected to an oil guide tube via another check valve, the oil guide tube is inserted into an inner oil chamber formed in a piston rod to form a closed circuit. The oil chamber of the pump is connected to an inner chamber of the hydraulic cylinder via a sequence valve and the inner chamber is connected to the outer reservoir via a check valve. When the maximum effect capacity of the oil chamber of the piston rod, a single touch of the pump can raise the hydraulic jack to the required loading position for raising at no load or light load conditions.