The invention provides high-flexibility aqueous acrylic acid polyurethane elastic resin, which is prepared by the following steps of: modifying an organic silicon monomer, an acrylic acid long-chain monomer and a hydroxyl monomer through specially designing a vitrification temperature of an acrylic acid monomer; synthesizing hydroxyl acrylic resin with the very low vitrification temperature; and compounding the acrylic resin and a multi-isocyanate curing agent to obtain the high-flexibility aqueous acrylic acid polyurethane elastic resin. According to the high-flexibility aqueous acrylic acid polyurethane elastic resin, the organic silicon monomer, the long-chain monomer and the hydroxyl monomer are adopted; hydroxyl type aqueous acrylic resin with the high flexibility is synthesized by specially designing the vitrification temperature; and the resin is matched with the multi-isocyanate curing agent to be used as a film forming material to prepare a self-drying type aqueous elastic coating which can be applied to the surface of a flexible plastic product.