Method for improving melt strength of polyester resin

The invention provides a method for improving melt strength of polyester resin. The method mainly comprises the following steps: A, preparing a copolymer intermediate containing active functional groups by taking a monomer containing active functional groups as a first monomer and taking another one or more monomers as a copolymerization monomer, the positions and quantities of active functional groups in the copolymer intermediate are exact; and B, coupling molecules of the polyester resin by using the copolymer intermediate containing active functional groups through liquor reaction or melt blending reaction, so that large molecules of polyester generate branched structures so as to improve the melt strength of the polyester resin. By adopting the method provided by the invention, the melt strength of the polyester resin can be greatly improved, and the branched polyester material prepared by the method provided by the invention can be applied to the fields such as foaming, melt spinning or thin film preparation.