The invention relates to a fixing jig. The fixing jig is used for fixing a workpiece, so that the workpiece is polished. The workpiece comprises a machined part and a non-machined part. The fixing jig comprises a base, an insert, a cover plate and a fastener, wherein a through groove is formed in the base, and the workpiece can be accommodated inside the through groove; a fastening hole communicating with the through groove is further formed in the base; the insert is arranged inside the through hole in a sliding mode; the base is covered with the cover plate, and a machining hole is formed in the cover plate; and the fastener can penetrate through the fastening hole and fix the mutual positions of the insert and the base. Compared with a traditional fixing jig, the fixing jig is advantageous in that due to the arrangement of the cover plate, the machined part and the non-machined part of the workpiece can be well separated, and thus the situation that the non-machined part of the workpiece is damaged when the machined part of the workpiece is polished subsequently can be avoided, and the polishing quality of the workpiece is improved.