To address the limitations of traditional harmonic analysis methods in identifying major tidal constituents from short-term current data,a comparative study is conducted using the tidal admittance method and the ratio-of-amplitudes method.Field observations from a typical cross-section in the lower Huangpu River during neap,medium,and spring tides are used.By fitting the normalized amplitude and phase lag of major constituents as functions of frequency,a smooth tidal admittance model is constructed and its predictive performance is evaluated.The results indicate that the admittance method,without relying on long-term data or empirical amplitude ratios,can effectively applied to the harmonic analysis and velocity prediction of short-term tidal currents.Compared with the ratio-of-amplitudes method,it reduces the root-mean-square error of current prediction by an average of 8.9%.Quadratic fitting further reveals a continuous relationship between frequency,the normalized amplitude and delay angle of diurnal and semidiurnal constituents,confirming the smoothness of the admittance function and its applicability in harmonic analysis.This method enhances short-term tidal forecasting and supports hydrological and engineering decision-making.