High-frequency pressure measurement is crucial for the safety analysis of Steam Generator Tube Rupture (SGTR) accident, through which the pressure values are obtained to assess accident consequences. However, the development of high-frequency pressure sensor operating at high-temperature lead bismuth eutectic (LBE) environments is still a challenging task due to the corrosion, insulation and sealing issues. Herein, we design a gas cooling device to reduce the LBE temperature near the pressure measuring point, enabling the high-frequency pressure measurement in harsh environment. To achieve the optimal structural design of the cooling device, simulation models of three cooling device structures were established and compared using CFD. The Keys relation for the turbulent Prandtl number (Prt) model was employed to analyze the heat transfer characteristics between LBE and the cooling gas. The effects of key structural parameters and gas inlet pressure on the cooling performance were analyzed. The results indicate that cylindrical ribs play a crucial role in improving the cooling effect by enhancing the disturbance on the cold side, where the measurement temperature reduces to a safe operating temperature of 329 °C, with a remarkable decrease of 45 °C. Smaller cooling ring and center-punched hole diameters, and higher gas inlet pressures enhance the cooling effect. Among these factors, increasing inlet cooling gas pressure is the most effective. As the inlet pressure was increased to 8 bar, the measurement point temperature significantly dropped to 292 °C. This study provides a practical solution for high-frequency pressure measurement in the high-temperature LBE pool.