Abstract: The high-value utilization of mixed dibasic acid by-products produced during the production of adipic acid has long been limited by bottlenecks such as high separation costs and low conversion efficiency. This article constructed a green and high-efficient catalytic conversion system: (1) Under mild conditions (70 °C, atmospheric pressure), a strong acid cation exchange resin was used to catalyze the esterification reaction to prepare high-purity dimethyl dibasic acid ester (DBE) with a purity of up to 99.95%; (2) The complex catalytic system constructed based on the coordination of triethanolamine with tetraisopropyl titanate promoted the ester exchange-polycondensation reaction of DBE with 1,4-butanediol or 1,5-pentanediol, and synthesized a series of polyester polyols with adjustable relative molecular weights (1000~5000). The obtained polyester polyols possessed excellent flexibility, compatibility and reactivity. This catalytic system not only provides an innovative strategy for the resource utilization of industrial by-products, but also has mild reaction conditions and high catalytic efficiency, offering a scalable solution for green chemical manufacture.