NOVELTY - The method comprises performing compound catalyzed hydrolysis on protein and performing chelation reaction on organic acid-amino acid and metal element, adding the plant and animal protein raw materials to the inorganic acid with certain concentration in proportion under normal barometric pressure and heating up to boiling hydrolysis, cooling down the obtained hydrolysate and adding the alkaline substance to neutralize, filtering and removing the impurity and then adding the amino acid stock solution, and concentrating and desalting the amino acid stock solution.    USE - The method is useful for preparation of microelement nutrient compound for improving activity of activated sludge in a waste water sewage treatment device.    ADVANTAGE - The method is capable of simply preparing the microelement nutrient compound with high efficiency thus improving the activity of activated sludge in waste water sewage treatment device.    DETAILED DESCRIPTION - The method comprises performing compound catalyzed hydrolysis on protein and performing chelation reaction on organic acid-amino acid and metal element, adding the plant and animal protein raw materials to the inorganic acid with certain concentration in proportion under normal barometric pressure and heating up to boiling hydrolysis, cooling down the obtained hydrolysate and adding the alkaline substance to neutralize, filtering and removing the impurity and then adding the amino acid stock solution, concentrating and desalting the amino acid stock solution, filtering the solution to obtain the purified amino acid mother solution, adding the microelement salt into the purified amino acid mother solution , adding microelement salt, which is 10-15% of the mother solution quality to the purified amino acid mother solution and heating up and keeping temperature at 70-90 degrees C, performing the chelation reaction for 3-5 hours to obtain composite microelement nutrient. The microelement liquid chelated by amino acid is spray dried to prepare the amino acid chelated composite microelement nutrient powder product. The method further comprises adding the plant and animal protein raw materials into the hydrochloric acid or sulfuric acid with a concentration of 20-45% to the solid-liquid mass ratio of 1:2 for constant boiling and hydrolyzing for 6-10 hours under the normal barometric pressure and at 100-155 degrees C, cooling the mixture at 50-65 degrees C, adding alkaline substance to neutralize until the pH value is 4.5-5.5, filtering and removing the impurity to obtain the amino acid stock solution, heating and concentrating the amino acid stock solution to be 1/3-1/2 of the stock solution amount, filtering, desalting and crystallizing to obtain the purified amino acid mother solution. The animal protein uses the animal keratin. The plant protein uses bean pulp.