Based on the meterological monthly rainfall dataset of 97 stations and ISCCP D2 data, using the SVD, statistical analysis and synthetic analysis methods, the relationships between nimbostratus, altostratus, deep convective cloud and precipitation and rain days are analyzed for 85 stations in Southwest China during summer of 1984 to 2005. The research results show that the summer nimbostratus is positively correlated with precipitation and rain days in Guizhou and Chongqing, especially the correlation coefficient with rain days reaches as high as 0.73. Except western and central Yunnan, there are obviously positive relations between summer altostratus and precipitation and rain days in the remaining parts of Southwest China, and the correlation coefficient is consistent with that of nimbostratus with percipitation and rain days. The results reflect that the pattern of altostratus and nimbostratus coexistence may favor the flood of those areas. At the same time, the correlation coefficients between deep convective cloud and precipitation and rain days are obvious in summer, and the correlation coefficients between deep convective cloud and precipitation is the bigger among those correlation coefficients and this correlation coefficient reaches as high as 0.86. It maybe because that deep convective cloud usually generates heavy rain showers and it makes a greater contribution to precipitation.