A thermal expansion valve comprises a valve body and a valve core member. The valve body is provided with a first connecting chamber, a lower cavity with a transmission member built in, and a first sealing member for separating the first connecting chamber and the lower cavity. A fifth pressure-bearing surface and a sixth pressure-bearing surface, pressed by a cold medium in the first connecting chamber in opposite directions, are disposed on a side wall of the valve core member. The first sealing member comprises a first flexible sealing element, disposed between the transmission member and an upper end portion of the valve core member and having a first edge portion connected to the valve body in a sealing manner. A sum of an effective stress area of a first pressure-bearing surface of the first flexible sealing element and a stress area of the fifth pressure-bearing surface is substantially equal to a sum of an effective stress area of a third pressure-bearing surface of the upper end portion of the valve core member and a stress area of the sixth pressure-bearing surface. Through the design of the structure of the thermal expansion valve, in an aspect, reliability of sealing between the valve body and the upper end portion of the valve core member can be ensured, sensitivity of the valve is improved, and difficulty of manufacturing the valve body and the valve core member can be reduced; and in another aspect, pressure influence caused by the cold medium in the first connecting chamber on the movement of the valve core member can be eliminated.