Using the precipitation derived by the CPC MORPHing technique (CMORPH) of the US National Oceanic and Atmospheric Administration (NOAA), the US National Centers for Environmental Prediction (NCEP) Climate Forecast System version 2 reanalysis (CFSv2), ERA-5 reanalysis obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF), and the Madden-Julian Oscillation (MJO) index of Wheeler and Hendon, effects of MJO on the rainfall persistence over eastern China in the summer of 2020 were analyzed. Based on the analyses of correlation, regression and wave source, three major conclusions were obtained as follows. 1) Compared with rainfall of the previous 21 years, the summer precipitation over eastern China in 2020 was extremely strong. This is because the summer monsoon rain belt has maintained for a very long time over southern China and the middle and lower reaches of the Yangtze River during 2020. 2) Meanwhile, a negative geopotential height anomaly in the middle and upper atmosphere, with the water vapor convergence between 1000-300 hPa and the instability at the lower levels, maintained over eastern China. Thus, the atmospheric circulation was in favor of the prolonged rainfall in the 2020 summer. 3) During this period, MJO was abnormally active in its phases 1 and 2 with significant period on 10-30 days, which indicates that MJO convective centers were sustained over eastern Africa and western Indian Ocean. Therefore, significant Rossby wave sources were found over eastern Africa and western Indian Ocean, which is consistent with the Gill mode. Finally, a Rossby wave train was excited at the sources and transported by the jet stream, and then induced the negative geopotential height anomaly over eastern China. Due to the sustain of the MJO in its phases 1 and 2, the negative geopotential height anomaly over eastern maintained and prolonged the rainfall in this region during 2020. The sensitivity experiments further prove that the 10-30-day signal is in favor of the formation of the negative anomaly of 500-hPa geopotential height and the positive anomaly of precipitation over eastern China.