Abstract: The daily high-resolution gridded station-observed rainfall over China and NCEP-DOE AMIP-II atmospheric reanalysis datasets for the period 1979-2015 are used to investigate the impact of the 30-60-day atmospheric intraseasonal oscillation (ISO) over the Asian monsoon region on persistent anomalous rainfall over the middle and lower reaches of the Yangtze River (MLYR). The interaction between ISOs over two sub-monsoon areas of South Asia and East Asia as well as the physical mechanism for the ISOs to jointly influence persistent extreme rainfall over the MLYR are revealed. Composite analyses demonstrate that the ISO over the South Asian monsoon region interacts with its counterpart over the East Asian monsoon region through upper-level divergent flows. During phases 1‒3 (5‒7) of the ISO, active (inactive) convection anomalies propagate northward from the equatorial Indian Ocean to the Indian Subcontinent‒Bay of Bengal. The accompanied divergence (convergence) anomalies in the upper troposphere cause anomalous convergence (divergence) downstream over the South China Sea‒western North Pacific (SCS‒WNP) through compensation effect, leading to anomalous descents (ascents) locally over the SCS‒WNP, and therefore is favorable for the development and persistence of anomalous inactive (active) convection anomalies. Such inactive (active) convection anomalies are characterized by prominent baroclinic divergence structure and further trigger a meridional-vertical circulation cell between the SCS and the Yangtze Basin, resulting in anomalous ascents (descents) and low-level moisture convergence (divergence) over the MLYR. As a consequence, positive (negative) rainfall anomalies continuously arise over the MLYR with the occurrence probability of extreme rainfall significantly increasing (decreasing), favorable (unfavorable) for the occurrence of persistent extreme rainfall events. Moreover, the intensity of ISO over the Asian monsoon region exhibits strong interannual variations and further modulates the frequency and duration of persistent extreme rainfall events over the MLYR. In strong (weak) ISO years, more (fewer) persistent extreme rainfall events occur over the MLYR and the duration is longer (shorter).