The invention is applied to the field of medicine biotechnology, and provides a vaccine adjuvant and application thereof as well as a vaccine against a porcine reproductive and respiratory syndrome. The vaccine adjuvant is water-soluble suspension liquid which is obtained by adding antimicrobial peptides, aluminium hydroxide gel, methionine, citicoline sodium glycine and a stabilizing agent into deionized water, wherein in the water-soluble suspension liquid, the concentration of the antimicrobial peptides is 0.5mg / mL to 2.5mg / mL, the concentration of methionine is 0.5mg / mL to 5mg / mL, the concentration of the citicoline sodium glycine is 0.5mg / mL to 5mg / mL, and the concentration of the stabilizing agent is 0.5mg / mL to 1.5mg / mL; the aluminium hydroxide gel is 10 percent by mass to 20 percent by mass of the water-soluble suspension liquid. By adopting the vaccine adjuvant disclosed by the invention, the differentiation proportion of M1 to M2 in macrophages can be induced, different typesof PRRSV (Porcine Reproductive and Sespiratory Syndrome Virus) virus strains can be killed, and meanwhile, internal organs are protected from being hurt. With combination of PRRSV killed antigens, the cellular immunity of organism can be improved, interferon is induced, and immunodepression produced by the PRRSV is reduced, so that a neutral antibody with high content can be produced quickly, themaintenance time is long, and viraemia of different virus strains can be reduced.