In this work, poly(ethylene succinate-co-0.3 m% ethylene oxalate-co-0.6 m% diethylene glycol succinate) (PEED) and poly(ethylene succinate-co-0.6 m% diethylene glycol succinate) (PED) with a similar weight-average molar mass (Mw) of about 6×104 g/mol were synthesized by a two-step melt polycondensation method to investigate whether the strong-acting ethylene oxalate groups in the molecular chain of poly(ethylene succinate) (PES) could improve the crystallization rate and physical properties of PES. As a result, PEED crystallized faster under isothermal melt crystallization condition and the density of PEED spherulites also increased, indicating ethylene oxalate significantly acted as a nucleating agent. Relative to PED, PEED presented a similar tensile strength, yet it's Young’s modulus increased by 13%, and elongation at break increased by 72%, indicating that 0.3 m% of ethylene oxalate could improve the physical properties of PES. This study provides a new strategy for improving the crystallization rate of PES.