Using the NCEP/NCAR Reanalysis and observed precipitation data from 1981 to 2019, the circulation characteristics of more ( less ) rainfall year in May in Shandong are classified, and the process of previous sea surface temperature ( SST ) affecting atmospheric circulation and further affecting precipitation is analyzed. The results show that in the typical more ( less ) rainfall year, the distribution of mid-high latitudinal circulations in Asia is “－, ＋” (“＋, －”). With dominated latitudinal ( meridional ) circulations, the east Asian trough is weak ( strong ). Early winter Kuroshio area and the tropical Indian Ocean SST are the key external forced factors that affects the precipitation in May. When the Kuroshio area SST is warm ( cold ), the 500 hPa height field is significant positive ( negative ) anomaly distribution, and the low-level wind field renders anomalous anti-cyclonic ( cyclonic ). Controlled by the southeast wind anomalies ( westerly ) in Shandong, the water vapor transport is strengthened ( weakened ), which is beneficial to more ( less ) precipitation. In a warm year of the tropical Indian Ocean, the 500 hPa height field in Shandong region is low in the west and high in the east, and the lower layer is dominated by the southeast airflow behind the anomalous anticyclone, which is basically consistent with the circulation characteristics of a typical more rainfall year, while the circulation in a cold year of the Indian Ocean is roughly opposite.