The invention belongs to the technical field of surfactants, and discloses a preparation method and application of a rhamnolipid composite surfactant. The preparation method comprises the following steps: adding lysozyme into rhamnolipid fermentation liquor which is totally fermented, conducting stirring and reacting under the conditions that a temperature is 45-50 DEG C and a pH value is 5-7, cooling the obtained fermentation liquor to room temperature, then adding APG, carrying out stirring and washing, then adding polyaluminum chloride, carrying out flocculent precipitation and centrifugation, taking a supernatant, and concentrating and drying the supernatant to obtain the rhamnolipid-APG composite surfactant. According to the preparation method disclosed by the invention, lysozyme is used for treating the fermentation liquor, and APG is used for washing, so the yield of rhamnolipid can be remarkably increased; and polymeric aluminum chloride is adopted to carry out flocculent precipitation on the fermentation liquor having been subjected to bacteriolysis treatment, so the purity of the product is improved. The obtained product has good surface activity, and has the advantages of being natural, environment-friendly, non-irritant and biodegradable when being applied to daily chemical washing products.