Aiming at aircraft airborne environment multi-parameter comprehensive testing requirements, by analyzing the theories and experimental results, a kind of fiber Bragg grating (FBG) gas pressure and temperature integrated monitoring method based on spectral reflectance characteristics identification is studied, and the dual parameter sensing mechanism as well as its theoretical model based on the diaphragm structure are also studied in this paper. OptiGrating software based on the coupled mode theory was used to simulate the reflection spectrum of the fiber Bragg grating sensor under different pressure and temperature conditions. Therefore, the characteristics of fiber Bragg grating sensor under different pressure and temperature conditions in simulate environment appeared. On this basis, with the aid of the flat diaphragm pressure sensitive structure enjoying a excellent elasticity and recovery performance, a diaphragm type double optical fiber gas pressure/temperature integrated monitoring system was constructed, and the package of the diaphragm type double fiber optic pressure/temperature sensing model was studied. Beyond that, the performance characteristics of the sensing model was also presented. A series of data analysis of the experiment showed that the strain sensing fiber Bragg grating reflection spectrum shifted to short wavelength direction under the condition of constant temperature with the increasing of the gas pressure, and the strain sensing fiber Bragg grating reflection spectrum sensitivity coefficient was about 0.803 0 nm·MPa-1. The reflection spectrum peak and the sidelobe level showed a good linear relationship with the pressure changing. When the air pressure was constant and temperature changed, fiber Bragg grating center wavelength sensitivity of temperature sensing fiber Bragg grating which was not affected by strain and only sensitive to temperature was about 9.39 pm·℃-1. However, when the pressure and temperature cross changed, micro pressure can be monitored in real-time under the condition of variable temperature. Fiber Bragg grating sensing by the inhomogeneous strain effect has certain chirp reflection spectra, the sidelobe peak wavelength of reflection spectrum will shift because of the change of temperature and pressure, which needs measurements at any moment in accordance with the monitoring environment. It has to be noticed that the temperature and pressure both have a good linear relationship with the fiber Bragg grating reflection spectrum center wavelength, and the spectral reflectance under different air pressure corresponding to the same order number sidelobe peak amplitude is equal. The above research provides a useful help for online comprehensive test of multi physical parameters in aviation spacecraft system.