Abstract: Traditionally, pressure altitude is obtained by the pitot-static tube installed on the surface away from the vehicle body. Free stream static pressure measured from the static pressure port located on the specific surface of the tube. And pressure altitude can be determined from the static pressure. While the measured static pressure data can be disturbed seriously near vehicle body, a new method based on the surface pressure data was developed to solve free stream static pressure instead of measuring it. Firstly, five pressure ports were configured on the nose surface, and pressure data set can be built based on CFD method. Secondly, according to relationship between free stream pressure and the pressure data set, free stream static pressure solution model and algorithm were developed. After free stream static pressure was solved, pressure altitude can be determined. Finally, system principle prototype integrated real time solving algorithm was developed, and wind tunnel and flight test was complemented to calibrate system performances. Calibration results show that, (1) Compared with wind tunnel, free stream static pressure differences between the air data system solving and wind tunnel provided are less than 0.25%. While for 2200 m low altitude, pressure altitude differences between the air data system and wind tunnel provided are less than 10～15 m. (2) Compared with the pitot-static tube, calibration data for the air data system developed in this paper was accurate enough to satisfy engineering demands. Pressure altitude differences between the air data system and the pitot-static tube are less than 10～50 m for 11000 m high altitude, and free stream static pressure differences between the air data system solving and the pitot-static tube measured are less than 1.2%. While for 1000 m ～2000 m low altitude, pressure altitude differences between the air data system and the pitot-static tube are less than 10～20 m, and free stream static pressure differences between the air data system solving and the pitot-static tube measured are less than 0.5%. Calibration data can provide data support for the future development of the FADS system.