The invention relates to a preparation method for anti-stress drug earthworm small peptide chelated chromium, which is characterized in that the live earthworms are cleaned, added with water and triturated by a high-speed triturator; then the earthworm triturate is mixed evenly to carry out the autolysis zymohydrolysis action so as to derive an earthworm small peptide liquid; the earthworm small peptide liquid is heated and inactivated by boiling water bath, and then is centrifugated for obtaining a small peptide concentrated peptide liquid; the earthworm small peptide concentrated peptide liquid is taken to be added with chromium trichloride for the chelation reaction; after being cooled and sterilized under the room temperature, the earthworm small peptide chromium chelateed compound is obtained; the earthworm small peptide chromium chelateed compound is concentrated by vacuum, added with mycoprotein powders to be absorbed, and treated by sponging drying; finally the earthworm small peptide chromium chelateed compound is crashed so as to be prepared into the earthworm small peptide chromium acid chelated compound. The preparation method for the anti-stress drug earthworm small peptide chelated chromium can improve the immunity of fish bodies and the inhibiting ability, enhance the high-temperature resistant ability, the high-intensity resistant ability and the infection ability for resisting the infection of aeromonas hydrophila, and raise the utilization ratio of chromium, while supplementing the nutrition of small peptide and improving the palatability of the feed and the anti-stress ability of the fish bodies to promote the growth of the fish bodies.