Abstract: Hydrodynamic regulation, as an effective restoration method of ecologically degraded shallow lakes, has attracted much attention. However, optimizing the hydrodynamic conditions to achieve the best repair effect remains a key scientific challenge. This study focused on a shallow lake in Nanning City, dividing it into hydraulically isolated experimental and control zones for a 36-day in situ comparative experiment. In the experimental zone, horizontal and vertical water circulation was achieved using a 100 m³/h circulating pump, while the control zone remained static. The study systematically investigated the effects of hydrodynamic conditions on the physicochemical properties and nitrogen cycling in shallow lakes. The results demonstrated that: (1) Compared to the static control zone, the experimental zone exhibited reduced fluctuations in water conductivity (EC) and dissolved oxygen (DO) concentrations during the 0-36 day experimental period, with decreased COD_Mn level. Surface water \mathrmNH_4^+ -N increased 1.83-fold while bottom water \mathrmNO_3^- concentration decreased by 45.09%, accompanied by a 24.84% reduction in total nitrogen (TN). (2) Hydrodynamic circulation disrupted the original aerobic-facultative-anaerobic stratification, thereby establishing a dynamic cycling system that enhanced water-nutrient exchange between surface and bottom layers. This significantly strengthened the coupled nitrification-denitrification process, effectively controlling nitrogen excessive accumulation and improving water quality and the ecological environment. (3) Based on the pollutant degradation rate, key parameters required for calculating the optimal circulation flow rate to achieve the desired denitrification efficiency in the study area were identified, such as water depth, area, and TN concentration in the experimental zone, providing a quantitative basis for hydrodynamic regulation. This study elucidates the critical role of hydrodynamic management in improving water quality in shallow lakes and offers novel theoretical and practical insights for aquatic ecosystem rehabilitation.