The invention relates to a nutrient of fresh sea cucumbers and abalone and a preparation method for the nutrient. The preparation method comprises the following steps of: removing viscera of sea cucumbers and abalone, cleaning, crushing, adding purified water, adding bromelain, performing enzymolysis, adding papain and performing enzymolysis; and filtering an enzymatic hydrolysate, and concentrating at low temperature and under reduced pressure to obtain the nutrient of the sea cucumbers and the abalone, wherein the nutrient is rich in sea cucumber short peptide, sulfated polysaccharides, saponin, and amino acids which are essential to human bodies. The content of the sulfated polysaccharides and the saponin of the sea cucumbers in the product is greatly improved; the decomposition rate of collagen of the sea cucumbers is improved from the traditional 60-80 percent to over 95 percent; the recovery rate of protein is improved from 50-65 percent to over 92 percent; the molecular weight of a polypeptide is reduced from 2,000-8,000Da to 500-2,000Da; the average peptide chain length is 2 to 10 degrees of polymerization; the content of the amino acids which are essential to the human bodies is increased, and particularly the content of arginine is increased; the full nutrition of the nutrient is improved; and the properties of active ingredients of the sea cucumbers and the abalone such as removal of free radicals, blood pressure reduction, senility resistance, tumor resistance, human immunodeficiency virus (HIV) resistance, liver protection and the like are strengthened.