A three-dimensional Princeton Ocean Model (POM) along with the observed hourly sea level data are used in this study to investigate the characteristics of the Tide-Surge Interaction (TSI) along the north coast of Sri Lanka in north Indian Ocean.In this study,the cyclone ‘Nisha’ 2008 case was selected and three numerical experiments were performed.The model reproduces reasonably well the tides,surges and total sea water levels and TSI water levels over the study region during this cyclone.The results show that the characteristics of the TSI are significantly shown along the northwestern coast of Sri Lanka.The maximum TSI intensity is associated with the strength and track of the cyclone.In this study,the maximum positive TSI reaches 0.6 m at hour 42 when the TC was strong.At hour 30 when the TC track was relatively weak,the maximum negative TSI reaches about -0.6 m.The magnitude of the interaction current (U_TSI) (0.2 m/s) and the direction of the U_TSI were observed significantly to flow out the northwestern coast.During the whole TC cycle,strong TSI occurs in the northwestern coast of Sri Lanka and the opposite coast of India,which indicates that the tidal effect cannot be ignored in the storm surge simulation in this region.