Based on remote sensing data, the characteristics and mechanisms of spatial and temporal variation of sea surface temperature (SST) in adjacent sea area of the Yangtze River estuary were studied with power spectrum and correlation analysis methods. The results show that the SST has an increasing trend of 0.48 ^°C/(10 a) from1982 to 2017 and significant oscillation periods of 10.0, 3.6, 2.4 and 1.0 years. Although the rising trend of SST exists in all seasons, the warming trend in spring is most significant while that in autumn is weakest. The SST increases from northwest to southeast in the area. In addition, the change in runoff of the Yangtze River has remarkable impacts on the SST variability, SST becomes warmer (cooler) when the runoff increases, and the impacts are most obvious in March, April and September. Atmospheric temperature above the Yangtze River estuary is significantly correlated with the SST. The general trend of atmospheric temperature has been rising, and this may cause the warming in SST due to positive heat flux from atmosphere to the sea through air-sea interaction.