Abstract: According to the tidal characteristic values obtained from annual observations at 12 hydrological stations in the coastal area of Jiangsu, two modified empirical formulas (Empirical Formula 1 and Empirical Formula 2) applicable to the sea waters of Jiangsu Province are proposed. The applicability of these two formulas and the existing empirical formulas (including Formula G.0.2 (simply called as Code Formula) in Appendix G of the Code of hydrology for harbour and waterway (JTS 145—2015) and Qiao Guangquan Formula) to the calculation of design water level in the Jiangsu sea area is evaluated. Combined with the mean tidal range obtained by numerical simulation calculations, the design water levels at the sites 30 km away from the coast in the Jiangsu coastal waters are calculated by using the four empirical formulas mentioned above, respectively. The results indicate that in calculating the Design High Water Level (DHWL), Empirical Formula 1 and Empirical Formula 2 deliver excellent applicability across the entire sea waters of Jiangsu Province, with the Mean Absolute Error (MAE) being lower than 0.10 m and the BIAS less than 0.02 m and featuring stable and credible predictions. By contrast, the Code Formula and the Qiao Guangquan Formula produce notably larger errors, with the MAE being 0.17 m and 0.23 m, repectively, and in the sea area of the core region of the radial sand ridges their computed values are 0.3-0.5 m lower than the actual values. In calculating the Design Low Water Level (DLWL), both Empirical Formula 1 and Qiao Guangquan Formula demonstrate a good applicability, with the MAE being all lower that 0.12 m and the BIAS less than 0.08 m. However, the Code Formula shows a poor fitting performance, with a coefficient of determination (R²) being only 0.62 and an MAE up to 0.34 m, leading to overly conservative computed outcomes. The research findings can provide a reference basis for determining design water level values in the coastal regions of Jiangsu Province.