NOVELTY - Preparing maggot protein feed comprises evenly mixing livestock residues with crop straws in a weight ratio of 1:2; adding fermented biogas slurry which accounts for one half of the mixture of the livestock residues and the crop straws, and carrying out anaerobic fermentation to obtain fly maggot culture media; stacking the fly maggot culture media in a strip on a wire side, putting fly blow on the fly maggot culture media, covering a layer of fly maggot culture medium on the fly blow, and cultivating maggots at an environment temperature of 20-25 degrees C; and collecting the maggots.    USE - The process is useful for preparing maggot protein feed (claimed).    ADVANTAGE - The process completely uses biogas slurry, which can cause environmental pollution, for fermenting the livestock residues and the crop straws, hence economical and ecofriendly.    DETAILED DESCRIPTION - Preparing maggot protein feed comprises evenly mixing livestock residues with crop straws in a weight ratio of 1:2; adding fermented biogas slurry which accounts for one half of the mixture of the livestock residues and the crop straws, and carrying out anaerobic fermentation to obtain fly maggot culture media; stacking the fly maggot culture media in a strip on a wire side, putting fly blow on the fly maggot culture media, covering a layer of fly maggot culture medium on the fly blow, and cultivating maggots at an environment temperature of 20-25 degrees C; and collecting the maggots to obtain the maggot protein feed, after the cultivating of the maggots is finished, collecting the fly maggot culture media on the wire side as an organic fertilizer for agricultural production. BIOLOGY - Preferred Process: The surface of the net-mesh has lengthx width product of 2 cmx 2 cm. The biogas slurry, after the completion of fermentation, is removed from the marsh gas tank. Preferred Components: The livestock residue is dairy manure, pig manure and/or chicken manure. The crop straw is wheat straw and/or rice straw.