Abstract: The distribution of three dimensions meteorological element fields of a heavy rain that occurring in the Southern China region was examined using a composite method. A mesoscale convergence line with some features of mini-cold front was a main system which caused the heavy rain. There was a weak downdraft at the rear of the heavy rain region at low level. It resulted in the divergent outflow at ground and a mesoscale cold region at low level. But at mid-and-high level,there was a warm region. The heavy rain region was between a large-scale low-level jei and high-level jet and showed the teudency of moving toward the maximum updraft region.