Weakly permeable saline-alkali soil is difficult to desalinate due to its high concentration of sodium ions, dispersed clay particles, and poor aeration and permeability. Under electric field conditions, the electric potential gradient has a significant impact on soil electroosmotic flow, pH change, and ion distribution. This paper investigated the effects of electric potential gradient on the water and salt transport characteristics of weakly permeable saline-alkali soil through indoor soil column simulation experiments, and studied the effects of different electric potential gradient treatments on the dynamics of water and salt discharge, desalination efficiency, alkalinization characteristics, and energy consumption. The experimental results showed that compared with the condition without electricity application, the treatments of 0.6, 1.2, 1.8, and 2.4 V/cm could improve the efficiency of water and salt discharge, and the efficiency increased with the increase of the electric potential gradient. During the 15-day electrification process, the amount of water and salt discharged in each treatment group was proportional to the electrification time, but the increment decreased with the electrification time. After 15 days of electrification, the desalination rates of the soils treated with 0.6, 1.2, 1.8, and 2.4 V/cm were 5.98%, 31.89%, 37.82%, and 51.64%, respectively, and the concentrations of water-soluble Na⁺ decreased by 6.34%, 30.71%, 32.07%, and 44.44%, respectively. In addition, pH value of the top 0-5 cm soil of the weakly permeable saline-alkali soil decreased to near neutral (6.93-8.03), and the adsorbed Na⁺ was basically removed. Based on the above research, the electric potential gradient treatment technology could not only accelerate the removal of salt and alkali from weakly permeable saline-alkali soil but also improve the alkalinity of the topsoil. Combining this technology with the abundant green energy such as wind and solar energy in the saline-alkali soil distribution areas of China provided an environmentally friendly and efficient technical solution for the improvement of saline-alkali soil.