Abstract: Fiber optic pressure and temperature sensing system are investigated based on Mach-Zehnder interferometer technology. Using all-fiber interferometer system, the variation of the optical power with pressure changing under various temperature conditions and temperature changing under the condition of pressure is measured and analyzed. The results show that the system's temperature measurement range is 39~46℃ in the absence of pressure and the system's temperature sensitivity is 4 078.7 nW/℃ when the temperature changes from 40 to 45℃ under 1N pressure. It has high temperature sensitivity and good linear relationship when it is 45℃, the sensitivity of optical power changing with pressure is 1.162 1 μW/N, the linear correlation coefficient is 0.989 3. Thus, it has better testing results of pressure and temperature in the range of 40~45℃ and 0~1 N individually.