The utility model relates to a hydraulic automatic temperature-control ventilator for road bed. The utility model can automatically control the air flow in vent pipes according to the change of the outside temperature and can effectively enhance the cooling effect of ventilating road bed, and also can avoid negative heating effect caused by the fact that summer warm wind enters into the vent pipes, and big temperature change around the vent pipes is avoided; the construction problems that high water road causes water freeze-thaw which can cause frostheave, thawcollapse, road bed settlement and influences the stability of road bed are avoided.