Using the observation and reanalysis data for the period of 1900-2014,this study shows that the impacts of Atlantic Zonal Mode (AZM) on the interannual variations of Australian autumn precipitation can be modulated by Interdecadal Pacific Oscillation (IPO).It is revealed that,when the IPO is in the positive phase,the AZM decreases the autumn precipitation in central Australia,whereas,when the IPO is in the negative phase,the AZM increases the autumn precipitation in central and southern Australia.The reason for this is that,during the IPO positive phase,the anomalous warming and ascending motion in the tropical Atlantic related to the AZM induce anomalous descending motion over the tropical eastern Pacific,thereby leading to anomalous upward motion around the Maritime continent.The anomalous upward motion adjusts the local Hadley circulation and results in anomalous subsidence in central Australia.This,together with the anomalous anticyclone in the lower troposphere,the southeasterly anomalies of which along the northwestern frame hinder the transport of warm and humid water vapor from the tropical Indian Ocean,results in a precipitation deficit in central Australia.In contrast,during the IPO negative phase,due to the different basic state and stronger AZM amplitude when compared to those during the IPO positive phase,the Rossby wave in the mid-high latitudes of the Southern Hemisphere caused by the AZM induces a barotropic cyclone in Australia.The anomalous cyclone not only trigger the anomalous ascending motion,but also contribute to the greater transportation of warm moisture from the tropical Indian Ocean to central and southern Australia,by means of the anomalous northwester lies along the northwestern frame,in turn leading to surplus precipitation in this region.Therefore,the IPO modulates the AZM-Australian precipitation relationship by altering the basic state and AZM amplitude.