Abstract: Multi-time-scale variations of summertime precipitation in Huaihe River basin during 1961-2016 are analyzed based on daily precipitation observed at 172 meteorological stations. Results reveal a significant quasi-biennial cycle in the entire study period and a decadal cycle since the 1990s. EOF analysis shows that the anomalies of summer precipitation in the basin are mainly represented by a uniformly more or less anomaly mode in the whole basin (the first leading mode), which explains about 37% of the total variance. Compared with precipitation in the middle and lower reaches of the Yangtze River, precipitation in Huaihe River basin has a poor relationship with the EAP teleconnection of 500 hPa geopotential height in East Asia, but has a much more significant relationship with the water vapor transport of southwesterly summer monsoon in the lower troposphere. Their correlation field displays an alternating positive-negative correlation wave trains from Somali Peninsula to Huaihe River basin. The wave trains indicate that when the Somalia cross-equatorial flow (SCEF) strengthens, the southwesterly moisture transport into Huaihe River basin increases due to the effects of the westerly winds over the tropical India Ocean, leading to water vapor convergence over Huaihe River basin in the lower troposphere and abnormally wet or flood climate there. On the contrary, dry or drought climate would occur when the SCEF is weak. The spatial correlation field between the SCEF and precipitation in China also shows that the most significant correlation region is located in Huaihe River basin. However, during the study period of this paper, the above relationship is not stable and exhibits an obvious interdecadal enhancement, indicating that the impact of the SCEF on summer precipitation in the basin has significantly enhanced in the recent two decades. This enhancement may be related to the changed relationships between the SCEF and the meridional water vapor transport on the southern side of Huaihe River basin and zonal water vapor transport on its western side, and the influence of the two water vapor conveyance belts on summer precipitation in Huaihe River Basin both have experienced interdecadal increase.