The present disclosure provides a collagen and sodium hyaluronate cross-linked composite filler for injection and a preparation method thereof. The collagen and sodium hyaluronate cross-linked composite filler is obtained by a cross-linking reaction of collagen and sodium hyaluronate with a 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) cross-linking system. As the EDC/NHS is used as a cross-linking agent in the present disclosure, the resulting product has no biological toxicity, so that the injury caused by a final product to an injection site and the human body is reduced. Meanwhile, due to intramolecular and intermolecular cross-linking, the degradation rate of the collagen and the sodium hyaluronate is reduced, and the retention time of the two in the body is prolonged. Therefore, the collagen and sodium hyaluronate cross-linked composite filler for injection in the present disclosure can be used in plastic surgery in the medical industry.