The invention, which belongs to the technical field of optical fiber sensing, relates to a fiber bragg grating soil pressure sensor comprising a sensor shell, a fiber bragg grating, an equal-strengthcantilever beam, an arc-shaped slideway, a primary diaphragm, a secondary diaphragm and a hydraulic cavity formed by connecting the components together. On the basis of a double-diaphragm structure, the two diaphragms are filled with hydraulic oil; a light steel ball is arranged at the free end of the equal-strength cantilever beam and the steel ball moves along the arc-shaped slideway under the action of soil pressure to cause the fiber bragg grating to generate strain; different arc-shaped slideways are designed according to different experiment requirements and the deformation degree of theequal-strength cantilever beam is manually controlled so as to control the deformation of the optical fiber Bragg grating pasted on the beam, so that the superiority of the optical fiber grating technology is brought into full play. A built-in temperature compensation grating is used for compensating the influence of temperature. The sensitivity and precision of measurement and the engineering applicability are remarkably improved.