The invention discloses a direct-acting overflow valve which comprises a valve body, wherein a cavity-bearing valve bush is arranged in the valve body; the bottom end of the valve bush is provided with a liquid outlet and a valve seat; the valve seat is provided with a liquid inlet; when the valve core abuts against the valve seat, the liquid inlet is disconnected from the liquid outlet; and when a pressure regulation spring is arranged between the end cover and the valve bush, the top end of the pressure regulation spring is connected with a regulating lever fixed to the end cover, and the bottom end is connected with a seal piston arranged on the top end of the valve core in the valve bush cavity, and a closed gas chamber, which is filled with a high-pressure gas, is formed among the seal piston, valve core and valve bush. According to the direct-acting overflow valve, the pressure regulation spring acts on the valve core through the high-pressure gas (air spring), so that the air spring is connected with the common spring in series; since the rigidity of the air spring is low, the overall rigidity after series connection is reduced; and since the air spring has the buffering and damping functions due to the compressibility of the air, the steady-state error of the overflow valve can be correspondingly reduced by reducing the pressure overshoot of the overflow valve.