The invention provides an adjuvant for vaccines. The adjuvant comprises polyacrylic acid polymer and cellulose ether, and further comprises an immunoenhancer. The adjuvant for vaccines provided by the invention can effectively promote effects of the vaccines, and not only can be used as an adjuvant for inactivated vaccines, but also can be used as a diluent for living vaccines. A vaccine composition containing the adjuvant is used for only once immunization to achieve the effect of twice immunization by using a commercial product, so as to greatly simplify the immune process and also avoid the occurrence of side effects; the adjuvant provided by the invention also makes protein stable without degradation or irreversible changes and can be used as a protein stabilizer.