Abstract: To predict the intensity of saltwater intrusion under different riverine discharge, a new empirical model was developed to predict the chlorinity in the upper South Branch of the Yangtze River Estuary, where saltwater intrusion is strongly affected by tidal flow from the North Branch. In the model, only runoff at Datong station and lunar calendar date were required as variables. Firstly, the changes of daily mean tidal range was investigated with measuring data at Xuliujing. Using the theory of harmonic analysis with 11 main tidal components, it was proved that the daily mean tidal range changes every half-month. Thus, a new method was proposed to estimate the daily mean tidal range by using the lunar calendar. Secondly, the quantitative relationships between chlorinity and riverine discharge, tidal range were developed using the measured data at Dongfengxisha. Some functions in previous empirical models were examined to test their effectiveness under the condition of saltwater intrusion from the sub-branch channel. Finally, an empirical model was proposed in the form of exponential function to describe the chlorinity under different riverine discharge and tidal range conditions. The predicted chlorinity process at Dongfengxisha was in good agreement with the observations, with the correlation degree of up to 0.8. Using the proposed model in this study, intensity of saltwater intrusion at a certain location can be estimated with simple input data, which provides a convenient method to conduct prediction of saltwater intrusion.