Thin-film composite membranes (TFC) comprised of polyamide have emerged as a promising candidate in molecular separations due to their ultrathin selective layer and controllable structure. However, improving selectivity while retaining satisfactory permeability of TFC membranes remains a great challenge. Herein, zwitterionic polyamide membranes have been fabricated for pervaporation dehydration via in-situ interfacial polymerization modification (in-situ IPM) strategy. In-situ amination of the substrates can improve the interface compatibility between the selectivity layer and the substrate through fourier transform infrared spectroscopy (FTIR) characterization, making the membranes more stable to resist the structural evolution in liquid conditions. The zwitterion modification afterwards endows the membranes with dense structure and improved hydrophilicity through X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and contact angle measurements. The optimized zwitterionic polyamide membrane with well-defined structure realizes superior separation performance with a separation factor of 3870 while maintaining a high permeation flux of 4380 g m⁻² h⁻¹ when processing 90 wt% ethanol aqueous solution at 76 °C, outperforming most reported TFC membranes. Moreover, the zwitterionic polyamide membrane also exhibits stable separation performance under the successive test. This work would provide a feasible scheme for the design of efficient TFC membranes for pervaporation dehydration.