The invention discloses a natural composite amino acid raw material preparation method. The method comprises the following steps: 1, taking cryopreserved fresh pig brain, unfreezing, cleaning, homogenating, adding the above obtained slurry to concentrated hydrochloric acid, uniformly stirring, and centrifuging to obtain precipitated brain proteins; 2, adding the precipitated proteins to sulfuric acid, hydrolyzing, adjusting the pH value to 7.5-8.5, and filtering to obtain an acid hydrolysate; 3, heating the acid hydrolysate, adding active carbon, separating, collecting the above obtained supernatant, and adjusting the pH value to 2.5-4.5 to obtain a crude extract liquid; 4, adding the crude extract liquid to a cation exchange column, adjusting the pH value to 6.5-7.5, eluting with ammonia water, collecting the obtained eluate, concentrating to remove ammonia water, adjusting the pH value to 6.5-7.5, and preserving at -20DEG C to obtain a frozen liquid; and 5, naturally unfreezing the frozen liquid, centrifuging, removing tyrosine and related impurities, collecting the newly obtained supernatant, carrying out ultrafiltration on the supernatant, collecting the obtained filtrate, and drying to obtain the desired natural composite amino acid raw material.