The invention discloses a multifunctional additive capable of strengthening the paper industry strength and a preparation method of the multifunctional additive. The multifunctional additive is prepared from the following components in parts by mass: 10-15 parts of an acrylamide monomer, 1.2-1.6 parts of ethoxy-modified acrylamide, 1.4-2.0 parts of one or more of an acrylic ester, a methyl acrylic monomer and an acrylic emulsion, an organic redox initiation system which accounts for 0.1-0.2% of total mass of monomers, 1.0-1.6 parts of an anionic monomer and 70-75 parts of deionized water. According to the multifunctional additive, a crosslinked fiber can react with an enhancer to form a three-dimensional network structure through adding the ethoxy-modified acrylamide, the acrylic ester, the methyl acrylic monomer and the acrylic emulsion, so that the action effect of the enhancer is finally improved, the physical strength of finished paper is strengthened, the enhancer has good anti-jamming capability and adhesive property through introduction of the anionic monomer, the retention and enhancement effects are improved, the content of a chemical additive in white water is reduced and sewage discharge is reduced.