Flying-wing aircraft are significantly influenced by the ground effect during critical flight phases—particularly during takeoff and landing. The accuracy of air data system is particularly important for flight control of flying-wing aircraft. This study investigates the impact of the ground effect on atmospheric parameter measurements using computational fluid dynamics (CFD) methods. A numerical model was developed to analyze the impact of relative height above ground, Mach number, and true angle of attack on the measurement accuracy of key atmospheric parameters, including static pressure, total pressure, angle of attack, and side slip angle. The results indicate that the ground effect has a pronounced influence on atmospheric parameter measurements for flying-wing aircraft. It is therefore recommended to apply adaptive ground effect corrections to atmospheric measurements by integrating simulation results, wind tunnel data, and flight test findings to enhance measurement accuracy and meet the demanding requirements for high-precision atmospheric data during the takeoff and landing phases.