The utility model discloses an optical fiber grating sensor. The optical fiber grating sensor comprises a support, an L-shaped arm support and an optical fiber grating. The L-shaped arm support includes a vertical arm and a transverse arm which are combined together to form an L shape. The L-shaped arm support is pivotally connected to the support through a pivot joint point on the vertical arm, and thus the L-shaped can rotate around the pivot joint point relative to the support. The transverse arm is provided with and adjustable mass block, wherein the position of the adjustable mass block on the transverse arm is adjustable so as to change the distance from the adjustable mass block to the vertical arm, and/or the mass of the adjustable mass block can be increased or decreased. An optical fiber of the optical fiber grating is fixed to the support at a first fixing point, and is also fixed to the vertical arm of the L-shaped arm support at a second fixing point. The grating structure of the optical fiber grating is positioned between the first fixing point and the second fixing point. The optical fiber grating sensor has a wide frequency response range and has adjustable sensitivity.