Based on TropFlux, ERA5 and HadlSST datasets from 1979 to 2017, this paper investigates the relationship between the North Atlantic Oscillation (NAO) and the sea-air heat flux in the tropical Indian Ocean in winter.Results show that the NAO index is negatively correlated with the net air-sea heat flux in the tropical Indian Ocean as a whole, which means that when NAO is in a positive phase, the ocean transfers heat to the atmosphere, and the significant region is mainly located in the tropical western Indian Ocean (10°S-10°N, 50°-70°E).The net air-sea heat flux anomalies are mainly contributed by the latent heat flux and shortwave radiation anomalies.The contribution rates of latent heat flux and shortwave radiation are 72.96% and 61.48% (71.72% and 57.06%) during the NAO positive (negative) phase events, respectively.NAO can affect the local atmospheric circulation in the Indian Ocean through Rossby wave train, and then affect the air-sea heat fluxes.When NAO is in a positive phase, the wave train propagates to the Indian Ocean along the mid- and low-latitude path, triggering an anomalous anticyclone circulation in the upper troposphere over the northern Arabian Sea.The anomalous anticyclone circulation enhances the Arabian high, which strengthens the northerly winds in the northern Indian Ocean and the cross-equatorial flow.With the increase of wind speed, the sea surface evaporation is enhanced.At the same time, the enhanced cross-equatorial flow leads to the stronger tropical convergence zone.The strengthening of deep convection leads to the increase of tropospheric water vapor and cloud cover, which further causes the decrease of downward shortware radiation.