The influence of the sea surface temperature in the Eastern Indian Ocean (EIOSST) in winter on the synchronous rainfall in the southern part of China was studied by using the NCEP reanalysis monthly data, sea surface temperature data, and the Chinese monthly precipitation data at 160 stations. It shows that EIOSST is closely connected with the precipitation in the southern part of China. As EIOSST in wintertime was warmer than usual, there would be more precipitation in the southern part of China. EIOSST affected the rainfall in the southern part of China by the perturbation in the area of the southern branch trough and moisture transportation. As the eastern Indian Ocean was warmer than usual, the local convection and ascending motion enhanced. Thus, the perturbation in the area of the southern branch trough intensified. As the intensified perturbation moved eastward, the water vapor transport from the Bay of Bengal to the southern part of China strengthened, leading to more precipitation in that area. Further analysis shows that the influence of EIOSST on the southern branch trough and the precipitation in the southern part of China was consistent with ENSO, but it was weaker and was independent of ENSO. If the effects of EIOSST and ENSO were consistent in one year, there would be a distinctly anomalous precipitation in the southern part of China.