The fermentation method for preparing SA is distinguished by low energy consumption and environmental friendliness, but the resulting products mainly exist in form of disodium succinate (DSA). Direct esterification of DSA using CO2 and CH3OH as esterification reagent to produce dimethyl succinate (DMS) can avoid use of inorganic acids in downstream esterification industry of bio-based DSA. On basis of high-resolution mass spectrometry analysis and quantum theoretical calculation, the process of DSA direct esterification involved sequentially forming 3-carboxypropanoate, monomethyl succinate (MMS), and DMS. Furthermore, the reaction kinetics of DSA direct esterification was investigated by experiment and numerical simulation method, where the reaction kinetics equation and reaction rate constant were obtained. The activation energy for the generated process of MMS by DSA was 37.15 kJ/mol, while the one for the formed process of DMS from MMS was 85.80 kJ/mol, indicating the latter was the speed control step of DSA direct esterification.