Abstract: Meiyu front plays an important role in summer precipitation in Central China. Based on the GMS-5 satellite images, NCEP reanalyses (2.5°×2.5°) and final analyses (1°×1°) data, and meteorological conventional sounding observations, the horizontal and vertical structures of meiyu front are summarized using multiple diagnostic variables (including wind, temperature, jet streak, frontal area, pseudo-equivalent potential temperature, divergence, vertical motion, static instability, etc). In this paper, four cases of meiyu front were selected and analyzed, two of them are on 26-28 June and 23 July 2002 during the Experiment on Heavy Rain in meiyu Front in the Downstream of Yangtze River, and the other two casesare in May and July 1998. The two cases in July of 1998 and 2002 are the secondary meiyu front cases. The results show that the structures and characteristics of the meiyu front are different for various cases, or at various places and time, or at variious stages of one case, and the frontal characteristics can be transited from the polar front to the equatorial front. Due to the interaction of the different scale circulations in the high and low latitudes, the horizontal structures of the meiyu front are plenty of various forms.The results in this paper also show that the typical meiyu front consists of a narrow band with high gradient of equivalent potential temperature below 500 hPa, south of which is warm and moist air mass, and north of which is the indifferent air mass from the mid-latitude ocean or the polar continent. Below the mid troposphere, south of the front blows southwest wind, and north of the front the easterly. The ascending motion and precipitation usually occur ahead of the meiyu front. In the upper troposphere, the subtropical front is above the meiyu front, but they are not connected. In addition, the upper westerly jet and the easterly to the south of the meiyu front consist of the upper divergent flow field.The multi-scale characteristics of the horizontal structure of meiyu front can be summarized as follows: in the upper troposphere, there exist the subtropical westerly jet, the easterly to the south of meiyu front, and the South Asia high; at the mid tropospheric 500 hPa, the subtropical high over the west Pacific is the main weather system, and there are also some short wave troughs in the north; in the lower troposphere, the planetary scale southwest monsoon, the large scale low level southwest jet, and the meso-scale vortex or waves near the shear line are associated with the meiyu front.