Abstract: Based on annual tidal characteristic observations from 12 hydrological stations along the Jiangsu coast, this paper evaluates the applicability of existing empirical formulas for calculating design water levels in the Jiangsu sea area, including Formula G.0.2 in Appendix G of the Code of hydrology for harbour and waterway (JTS 145—2015) and Qiao Guangquan’s formula. Two revised empirical formulas (Empirical Formula 1 and Empirical Formula 2) tailored to the Jiangsu sea area are proposed in this study.Combined with mean tidal range results derived from numerical modelling, design water levels at locations 30 km offshore along the Jiangsu coastline are calculated using the four aforementioned formulas respectively. The calculation results indicate the following conclusions: For Design High Water Level (DHWL) estimation, Empirical Formula 1 and Empirical Formula 2 deliver outstanding applicability across the entire Jiangsu coastal waters, with the Mean Absolute Error (MAE) below 0.10 m and BIAS less than 0.02 m, featuring stable and credible predictions. By contrast, the Code Formula and Qiao Guangquan formula produce notably larger errors, with respective MAE values of 0.17 m and 0.22 m; their computed values are 0.3–0.5 m lower than the actual values in the core region of the radial sand ridges.For Design Low Water Level (DLWL) calculation, Empirical Formula 1 and the Qiao Guangquan formula exhibit favourable performance, with MAE below 0.12 m and BIAS less than 0.08 m. However, the Code Formula shows poor fitting performance, with a coefficient of determination (R²)) of only 0.62 and an MAE up to 0.34 m, leading to overly conservative computed outcomes.The research findings can serve as a technical reference for the determination of design water levels in coastal Jiangsu.