Abstract: To better understand the synoptic cause of water-logging process at milk-ripe stage of summer maize, and provide better service to meteorological disaster prevention and mitigation in Henan, NCEP/NCAR 2.5°×2.5° reanalysis daily average data and conventional meteorological observation data were used to analyze the circulation conditions and characteristics of temperature, humidity and wind of a high-impact and longstanding water- logging process. The results showed that: (1) the water- logging process had a significant circulation characteristic, which meant upper troposphere stably maintained unusual high-wedges over the Ural Mountains and the Okhotsk Maintains constantly as well as unusual low-trough over the Balkhash Lake and Japan; the jet stream on 200 hPa happened and maintained; south Asia high maintained eastward and northward as well as subtropical high maintained westward; (2) a low boundary-layer-easterly wind happened and maintained during the progress, the beginning and ending of easterly wind corresponds with the rainfall; the enhancement and unusual change of easterly wind cooperating with the unusual- warm on 700 hPa corresponded with obvious rainfall increase; (3) average and anomaly height on 500 hPa along 50°E-time section (Figure 55) could be used in prediction of the continuous-rain’s beginning and maintaining time in medium time.