Reasons of serious drought in eight cities and provinces of Northern China in 1942 were analyzed. Results indicated that there is an extreme arid event occurred in 1942 and centering on Henan Province, which occurred under a relatively warm background. The arid event was the most serious during the summer and winter. The warm sea temperature of Pacific Ocean during 1942 was the most important sea background of this extreme arid event was, while the negative phase of South Oscillation during 1940-1942 was the most outstanding circulation environment of this extreme arid event. In addition, the El Nino event with the intensity of 1 level, the weaker East Asian summer monsoon, and the less landing typhoon than the other years possibly could be the main reasons inducing to this extreme arid event in 1942 over the north China. Because Henan Province is the climatic change sensitive area and the ecological environment frail area, the earlier period dry waterlogging disaster frequency sends, in addition the multi-disasters were in the past concurrent, caused Henan Province's drought to be most serious in 1942.