[Objective] Water-blocking ratio is an important indicator for assessing the impact of water-related project construction on river flood discharge. For meandering and wandering rivers whose flow cross-sections are curved, conventional water-blocking calculation methods are not applicable. [Methods] By setting a threshold for the flow direction deviation angle, sections of non-orthogonal water-related projects along the curved river cross-sections were divided into local cross-sections within a certain range of flow direction variation. The local project water-blocking area was calculated within each local cross-section. A non-orthogonal water-blocking calculation method for curved river cross-sections was proposed, and was applied to the calculation of water-blocking ratio of Dongjing River Bridge on Wuhan-Songzi Expressway. [Results] When the curved river cross-section at Dongjing River Bridge was divided into 116 local flow cross-sections, the total water-blocking area was 975 m², and the water-blocking ratio was 4.24%. The rationality of the water-blocking ratio calculation was analyzed using an empirical formula and a two-dimensional mathematical model. According to the water-blocking ratio and Henderson formula, the water level rise in the river channel was calculated to be 1mm, which was consistent with the 1-3 mm rise at the pier position calculated by the two-dimensional numerical model. As the average velocity of the entire cross-section was used in the empirical formula, it was reasonable that the calculated water level rise was slightly smaller than the local rise at the pier position calculated by the two-dimensional numerical model. [Conclusions] It is feasible to calculate the water-blocking area and water-blocking ratio of non-orthogonal projects in curved rivers by dividing them into local flow cross-sections, which can provide a reference for water administrative departments in approving river-related construction projects regarding their flood discharge impact.