<p>Ocean-degradable polyesters incorporating hydrophilic and rapidly degradable glycolide (GL) units into the polymer chain are the most promising for addressing marine plastic pollution, however, it is challenging to obtain high-molecular-weight copolymers with narrow molecular weight distributions. Herein, we prepared a novel biodegradable material, poly(butylene succinate-<i>co</i>-glycolide) (PBSGL), through ring-opening copolymerization using glycolide, succinic anhydride, and 1,4-butanediol as raw materials, providing a new solution strategy for marine pollution. GL could be polymerized according to the pre-designed composition by ¹H-nuclear magnetic resonance (¹H-NMR) and gel permeation chromatography (GPC) results, indicating controlled polymerization with the synthesized PBSGLs having a weight-average molecular weight of up to 12.30×10⁴ g/mol and a narrow molecular weight distribution (1.33–1.65). Differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) results showed that <i>T</i>_g of PBSGLs increased from −32.5 °C to −26.5 °C with the increase of GL content from 0% to 40%, while <i>T</i>_m (&gt;76 °C) was much lower than <i>T</i>_d,5% (&gt;314 °C), which indicated that PBSGLs had good thermal stability and expanded the processing window and application range of the original poly(butylene succinate) (PBS) materials. Under simulated difficult conditions, PBSGL copolyesters could degrade faster with increasing GL content, where PBSGL40 degraded by 22.6% in 12 days, showing good biodegradability. Currently, most biodegradable polyesters with good performance slowly degrade in seawater. In a 30-day artificial seawater degradation test, the amorphous PBSGL40 copolyester showed a about 15-fold (2.33% weight loss) improvement in degradation ability compared to pure PBS, demonstrating rapid seawater degradation capability.</p>