<p>A high-temperature and high-pressure valve is the key equipment of a wind tunnel system; it controls the generation of high-temperature and high-pressure gas. To reduce the adverse impact of high-temperature and high-pressure gas on the strength of the valve body, a cooling structure is set on the valve seat. This can significantly reduce the temperature of the valve body and valve seat. The effects of its structure on the cooling characteristics and stress of the valve seat are studied, and six main parameters that can completely describe the geometry of the cooling structure are proposed. The central composite design method is used to select sample points, and the multi-objective genetic algorithm (MOGA) method is used for optimal structural design. A modification method according to the main parameters for the valve seat is proposed. The results show that the cooling structure weakens the pressure-bearing capability of the valve seat. Among the six main parameters of the valve seat, the distance from the end face of the lower hole to the <i>Z</i>-axis and the distance from the axis of the lower hole to the origin of the coordinates have the most obvious effects on the average stress of the valve seat. An optimum design value is proposed. This work can provide a reference for the design of high-temperature and high-pressure valves.</p>