An injection mold and a device for preparation of a light guide plate are provided by embodiments of the present disclosure. An injection mold, comprising a male mold and a female mold which cooperate with each other to define collectively a molding cavity adapted for molding a sheet component therein; a blowing device is provided in the male mold and configured to blow out gas with a predetermined pressure towards a bottom surface of the sheet component molded in the molding cavity to overcome at least partially a vacuum adsorption force between the bottom surface of the sheet component and an internal bottom surface of the molding cavity such that the sheet component is separated from the male mold. Therefore, the sheet component can be demoulded successfully and prevented from a relatively large warping deformation during a demoulding process such that the quality thereof can be guaranteed.