Abstract: Addressing the challenge of efficient purification and reuse of saline-alkaline farmland tailwater contaminated by complex salinity-alkalinity and eutrophication, this study developed and constructed an electrodialysis (ED)-capacitive deionization (CDI) integrated system. Using ditch drainage from paddy fields in the Yinbei Irrigation District as the target wastewater, an orthogonal experimental design was employed to systematically investigate the effects of operational factors, including voltage, initial electrical conductivity, electrode spacing, and other factors on treatment performance. Key influencing factors were identified through range analysis and analysis of variance (ANOVA), and the optimal parameter combination was determined using the entropy-weighted TOPSIS method. The results showed that voltage was the primary factor influencing desalination efficiency, electrode spacing was the key factor affecting turbidity removal, and both initial electrical conductivity and voltage significantly regulated the effluent pH (P < 0.05). Under the optimal operational conditions (water temperature: 25.7 °C, flow rate: 2.0 L·min⁻¹, initial electrical conductivity: 2.30 mS·cm⁻¹, water depth: 8.5 cm, electrode spacing: 15 cm, voltage: 48 V, electrode diameter: 12 mm, anode-cathode distance: 30.0 cm), the removal efficiencies of total phosphorus (TP), chemical oxygen demand (COD_cr), and total nitrogen (TN) reached 97.10%, 90.00%, and 48.29%, respectively. Compared to the raw water, the salinity and turbidity of the effluent were reduced by 88.33% and 97.30%, respectively, with a pH of 6.43. The system achieved a water recycling efficiency of 69.12% and a desalination capacity of 1259.9 g·m⁻³. In conclusion, the integrated ED-CDI system enables deep desalination and synergistic removal of nutrients from saline-alkaline farmland tailwater. This approach contributes to enhancing water resource recycling efficiency and controlling agricultural non-point source pollution in arid regions.