Abstract: Based on the matching principle of soil medium and pressure transducer, a circular flat diaphragm with flexure of sheet structure fiber Bragg grating (FBG) soil pressure sensor was designed. By designing two symmetric fix ends on the diaphragm, we could successfully solve the problem that the reflection spectra of the FBG subject to the transverse force split in two main peaks. As the same time, for the strain effect caused by the fix ends-flare angle, the sensor-s pressure sensitivity was enhanced dramatically. By analyzing the sensor-s enhancement effect theoretically, we got the sensor-s pressure sensitivity formula. Computed result showed the sensor-s pressure sensitivity was 1374.3 pm/MPa. ANSYS was used to establish the finite element model for the flexure of sheet structure. By extracting the displacement of fix ends- coordinate point on the fiber-s direction, we got the finite element model-s pressure sensitivity about 1360.8 pm/MPa. ANSYS analysis result has high entropy with theoretical analyis- conclusion and the relative error is 0.98%, which verifies theory design and analysis.