In this study, we propose a novel optical fiber pressure sensor based on fiber Bragg grating (FBG). This sensor is simple and has the advantages of being robust and inexpensive. The optical fiber pressure sensor consists of an embedded FBG sensor and an acrylonitrile butadiene styrene (ABS) rectangular cuboid structure. A numerical analysis model of an ABS structure under various pressure loadings is also presented in this paper. A pressure calibration test is carried out to examine the strain variations of the optical fiber pressure sensor at various hydraulic pressures. From the experimental results, the hydraulic pressure is from the 0–10 bar; the pressure sensor will change the wavelength conversion with a variable of 380 με. The proposed optical fiber pressure sensor shows a good linear relationship between the water pressure loading and the wavelength shift.