The impacts of MJO on springtime precipitation over East China has been analyzed with reanalysis data. It is found that rainfall tends to increase in MJO phase 3 and decrease in phase 7 over Yangtze River and its southern area. The circulation anomalies associated with the rainfall changeswith MJO phases appear to be linked to a zonal band of atmospheric convergence anomalies in mid-to-lower level atmosphere extending from northeast India to Yangtze River and the subtropical West Pacific when the tropical MJO convection moves eastward from phase 1 to 4. The convergence anomaly reaches maximum in MJO phase 3 over East China. The convergence will induce a cyclonic Rossby wave source through the vortex stretching term, promoting cyclonic circulation in mid-to-lower level atmosphere over East China. This provides a dynamical explanation linking the tropical convection anomaly and the rainfall increase over Yangtze River and its southern area during MJO phase 3. The impact of MJO phases on rainfall prediction skill has also been investigated in a modern sub-seasonal to seasonal prediction system. The correlation between rainfall from the reanalysis and from the prediction tends to increase in MJO phases 3 and 7 when the MJO impact is the strongest.