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Three kinds of Keggin-type titanium-based polyoxometalate-ionic liquid catalysts were prepared, and the chemical structure, crystal structure and thermal stability of the three catalysts were analyzed and tested by infrared spectrometer, ultraviolet-visible spectrometer, X-ray diffractometer, and thermogravimetric analyzer, respectively. Afterwards, their performance in catalyzing the coupling reaction of ethylene carbonate (EC) and dimethyl succinate (DMSu) to synthesize polyethylene succinate (PES) was studied, and the effects of different metals on the catalytic performance and the mechanism of action were discussed. The optimal process parameters for the coupling reaction were explored. Finally, the chemical structure of PES was characterized by infrared spectrometer. The results show that under the same process parameters, the polyoxometalate-ionic liquid catalyst Bmims [Ti(H2O)TiMo11039] had the best catalytic effect. Under the optimal process parameters, Bmims [Ti(H2O)TiMo11 O39] had obvious inhibitory effect on side reactions, and the yield and selectivity of PES prepolymer were up to 72. 23% and 88. 64%. [ABSTRACT FROM AUTHOR]