In autumn 2020, China’s climate presented the features of “warmer and wetter” than normal. But the intra-seasonal variability was significant. The distribution of precipitation anomaly shows rainfall was more than normal in south and less than normal in northern part of China in September, and the pattern was reversed in November. The circulation of mid-high latitudes of Eurasia in autumn was in the “+-+” EAP pattern, which also showed obvious intra-seasonal variability. The subtropical high over western Pacific (WPSH) continued to be stronger, larger and more westward, but developed southward to its climate state in September and northward in October-November. Further analysis proves that wide warming in the tropical Indian Ocean Basin was beneficial to the strong, large and westerly features of WPSH in autumn. The evolution of SST over tropical mid-east Pacific, where El Ni〖AKn~D〗o event ended in spring and La Ni〖AKn~D〗a started in autumn, had an important impact on tropical and subtropical circulations and favorable to the northward of WPSH, especially in October. Convective activity in the western Pacific warm pool was significantly weaker and more southward than normal, which was conducive to the southward WPSH in September. The co-action of SSTA evolution and intra-seasonal variability of tropical convective activity led to the significant intra-seasonal variability of precipitation in autumn 2020.