Mainly using the observational data and the 1.5×1.5 latitude-longitude grid data obtained by Gaussian weighted interpolation, this paper analyzes the monsoon stream tube during the seven occurrences of extensive torrential rainfall over the Jiang-Huai Area in June-July of the years from 1983 to 1986. Based on the analysis, the planetary scale and mesoscale systems in the monsoon stream tube are separated by the smooth filtering method and calculation is made of the vortieity, divergence and vertical velocity fields and their evolution.Results show that the monsoon stream tube is an east-west continuous monsoon vertical circulation system. The filtering method contributes to farther understanding the features of multi-scale systems and their interactions. It is pointed out that the mesoscale system in the monsoon stream tube is very active and has a direct influence on the tube itself as well as the location and intensity of the corresponding heavy rain and rain belt. This study helps to reveal the mechanisms of the monsoon heavy rain and rain belt and is expected to improve the weather forecasting.