The invention relates to a method using an antibacterial composition extracted from tachypleus amebocyte lysate waste to prepare cosmetics. The method includes the steps of firstly, extracting the antibacterial composition from the tachypleus amebocyte lysate waste, to be more specific, collecting discarded emulsion sediments and discarded plasma in tachypleus amebocyte lysate production, using the discarded emulsion sediments to prepare crude tachyplesin peptide extract, using the discarded plasma to prepare crude hemocyanin extract, using the discarded plasma to prepare crude SOD extract, and mixing the three crude extract to prepare the antibacterial composition; secondly using, by mass percentage, 30-50% of antibacterial composition, 2-4% of olive oil, 1-2% of vitamin E acetate, 0.5-10% of diethylene glycol fatty acid ester, 0.1-10% of shaping thickening agent and the balance deionized water to prepare cosmetic components, and preparing the cosmetics according to a preparation process. The method has the advantages that prepared cosmetics can effectively inhibit the growth the bacteria and fungi, is safe, mild and free of toxic and side effect, has multiple effects of resisting bacteria, diminishing inflammation, moisturizing the skin and preventing ultraviolet and can slow down skin aging.