Based on the monthly NCEP/NCAR reanalysis data during 1978—2012, this paper studies the precursor of the summertime anomalous circulation to the south of Lake Baikal.Results show that the convection from Indonesia to western Pacific in the preceding winter, consistent with the summertime anomalous anticyclonic circulation to the south of Lake Baikal, is one of the precursors to predict the summertime anomalous circulation to the south of Lake Baikal.When the convection is stronger from Indonesia to western Pacific in the preceding winter, the convection moves northward to the western flank of Tibetan Plateau in summer, which is beneficial to the occurrence and maintenance of the anomalous anticyclonic circulation to the south of Lake Baikal.However, when the convection is stronger in the western Indian Ocean in summer, the convection from Indonesia to western Pacific in the preceding winter is not consistent with that in the western Tibetan Plateau in summer.The stronger convection in the western Indian Ocean weakens the impact of the upward motion in Tibetan Plateau and its western part on the circulation in Lake Baikal, which is against the formation of anomalous anticyclonic circulation to the south of Lake Baikal.Therefore, when the convection is weaker in the western Indian Ocean in summer, the convection from Indonesia to western Pacific in the preceding winter corresponds well with the summertime anomalous circulation to the south of Lake Baikal.When the convection is stronger in the western Indian Ocean in summer, the above relationship will be changed.