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This paper aims at investigating the climate-mean integrated moisture transport (MT) of troposphere for 1971 similar to 2000 and the relationship between moisture divergence an:I seasonal precipitation in East Asia. The results made from ERA-40 shows that the spatial pattern of the precipitation approximately coincides with large-scale moisture divergence. A further decomposition manifests that the monthly-wind moisture transport (MMT) plays the dominant role for seasonal divergence patterns. The MMT convergence areas approximately fit in the big precipitation areas, while the MMT divergence almost covers the arid and semi-arid zones in northern China and Mongolia. The transient eddy moisture transport (EMT) is about ten-time smaller than MMT’s in magnitude and plays a key role in moisture transport northward for non-monsoon period. Usually, EMT divergence is of inverse phase to MMT’s, suppressing the MMT impact on precipitation in summer monsoon zones, and it is the major one that supplies water vapor to the precipitation in arid and semi-arid zones. However, their divergences are compatible and overlapped in phase around the phase transition belt of the MMT divergence. It turns out that large-scale precipitation characteristics greatly rely on competence of MMT and EMT, being the physical cause that lead to specific pattern of the large-scale precipitation. Besides, the mechanism of regional climate formation also implies the mechanism of regional precipitation change. A case study shows that the severe floods in both Yangtz River and Songhua-Nen rivers basin in 1998 resulted from anomalous MMT convergence of monsoon moisture transport, while both MMT and EMT divergences led to anomalous dry climate in the north and the northwest of China. In addition, it is the strong EMT divergence resulting in significant rainfall reduction in the south part of North China and the southeast coast of China. One could also make a further investigation on the causes leading to the anomaly of MMT or EMT, or both. This is a new way for exploring the mechanism of regional climate change.