Abstract: The plain river network area is connected with water systems, and there are many sluice pump projects. There are problems such as lack of guidance for water diversion and unscientific timing of water diversion in engineering scheduling. This study considers the monthly changes of the river water level and ecological water demand, and proposes a calculation method based on the appropriate ecological water level interval of the river to guide the diversion and drainage of the sluice pump project. Taking Tongzhou District of Nantong City as an example, the water level in the year was divided into three water level management periods, the appropriate ecological water level interval of the river was determined and corrected, the appropriate ecological water level was taken as the control target, and the current diversion and drainage volume of the project was adjusted. The results show that: (1) The high water level period is from July to October, with the suitable ecological water level range 1.77~1.99 m; the transitional period includes April to June and November, with the suitable ecological water level range 1.54~1.95 m; the low water level period is from December to March of the next year, with the suitable ecological water level range 1.46~1.77 m. (2) On the basis of meeting the suitable ecological water level interval, the water diversion needs to be increased by 287.56×10⁴ m³ and 399.56×10⁴ m³ in the middle and late June, and the water diversion volume should be reduced during the rest of the period, especially from July to September, and the water diversion volume should be reduced by 6 064.11×10⁴ m³. The suitable ecological water level calculated in this paper can objectively reflect the actual changes of river network water level during the year, which is convenient for the management of water conservancy departments. The given water diversion and drainage volume that needs to be adjusted under the constraints of suitable ecological water level can provide references for water diversion and drainage engineering scheduling in plain river network areas.