Polyester nanofiltration membranes typically outperform traditional polyamide alternatives in fouling resistance, water flux, and chlorine tolerance. However, their alkali resistance remains poorly understood. This study investigates the stability of polyester membranes, prepared via interfacial polymerization of eight hydroxyl monomers with TMC, in alkaline conditions (pH 12.4). We systematically recorded changes in water flux and solute rejection and employed SEM, AFM, zeta-potential, contact angle analysis, and XPS to examine physicochemical structural changes during hydrolysis. The findings reveal that most membranes are susceptible to alkaline hydrolysis, evidenced by increased water flux and decreased rejection rates. Specifically, membranes derived from pyrogallol-based hydroxyl monomers exhibited the greatest instability, whereas those incorporating sodium alginate demonstrated remarkable stability. After immersion in water, the water flux of the TA membrane increased from 8.4 to 21.2 Lm−2h−1bar−1 and the rejection rate decreased from 36.6 % to 12.1 %. the water flux of PG membrane was from 22.0 to 54.2 Lm−2h−1bar−1, while the rejection rate decreased from 60.2 % to 22.7 %. DFT calculations corroborate these observations, linking ester bond energies with membrane stability. This study not only advances our understanding of polyester nanofiltration membrane properties but also highlights critical vulnerabilities in alkali environments, guiding future improvements.