Abstract: A method for preparing high molecular weight polybutylene succinate includes: (a) using maleic anhydride (MAH) and C1-C4 alcohols to produce dialkyl maleates and water, in which dialkyl fumarate is calculated as dialkyl maleate of an equivalent mole. A reactive distillation process is used for the purification and obtains dialkyl maleates; (b) selective hydrogenation of those dialkyl maleates in the presence of high pressure hydrogen to produce the corresponding dialkyl succinates; (c) condensation of dialkyl succinates with mostly 1,4-butanediol (BDO) and other aliphatic diols to produce high molecular weight polybutylene succinates by adding catalysts.