The invention discloses a method for preparing a laying hen feed additive for calcium supplement by using penicillin residues and a preparation method of the feed additive and in particular relates to the method for preparing the laying hen feed additive for calcium supplement by using the penicillin residues. The method comprises the steps of weighing the penicillin residues, adding wheat bran, potassium dihydrogen phosphate and magnesium sulfate, uniformly mixing by adding water, carrying out moist heat sterilization at the temperature of 100 DEG C, cooling, inoculating candida lambica seed liquid to a solid medium, fermenting in a constant-temperature tank for 66-72 hours, sunning in sunlight, crushing, uniformly mixing the crushed material and a dried-powder of housefly larvae according to the mass ratio of 8:2, and pelleting to obtain a finished product. The laying hen feed additive contains rich vitamin D, is capable of increasing the absorptivity of a laying hen to calcium and can be used for effectively preventing and treating laying hen calcifames.