During the spring of 2015, the air temperature over most China was above normal and the mean precipitation over China was near normal with strong intraseasonal variations in South China. In the early spring (March to April) of 2015, precipitation in South China was below normal, and after the arrival of the prime rainy season in the late spring, precipitation in the region was significantly above normal. Analysis shows that the later arrival of prime rainy season is related to the El Ni〖AKn~D〗o event, which induced the westward extension of the western Pacific subtropical high (WPSH) and prevented the water vapor from transporting to South China. After the arrival of prime rainy season, the transport passage of the water vapor to China via Indian Ocean is built up, accompanying the development of Somali crossequatorial flows, and the transportation has a northward shift resulting from the WPSH in the South China Sea. Moreover, the Indian Ocean is warmer than normal in the late spring, inducing the development of the lowlevel anticyclonic anomaly over South China Sea and the intensification of water vapor transportation. The two elements are likely the causes for the abnormal precipitation in South China.