The invention discloses a system and a method for determining a fiber fracture surface rate of an impact specimen fracture. The method comprises the following steps: step (1), acquiring an image meeting pre-set definition requirements of the impact specimen fracture by adopting a fracture fiber fracture surface image acquisition device of the impact specimen fracture; step (2), converting the acquired image of the impact specimen fracture into an impact specimen fracture gray level image, and carrying out enhanced region characteristic algorithm processing on the impact specimen fracture gray level image; step (3), generating a binarization image; removing speckles from the binarization image to obtain a fracture surface original cross-sectional area and an area surrounded by a crystalline region boundary; step (4), solving a difference value of the original cross-sectional area of the impact specimen fracture surface and the area surrounded by the crystalline region boundary; solving a specific value of the obtained difference value and the original cross-sectional area of the impact specimen fracture surface, and acquiring the fiber fracture surface rate of the impact specimen fracture. With the adoption of the system and the method, provided by the invention, the crystalline region boundary can be automatically found and the working efficiency is improved.