Abstract: Applying satellite cloud images and the conventional observations,the rainstorm in Yunnan province on June 26,2009 caused by MCC(Mesoscale Convective Complex) has been analyzed in light of large-scale environmental field and physical quantity.The results show that MCC was the directly influencial system to the rainstorm.The life cycle of MCC from generation,maintaining to disappearing was about over ten hours.MCC occurred in 500 hPa trough area between south-east of Sichuan and east of Yunnan and 700 hPa south-east of shear line.The atmospheric total energy gradually increased,unstable energy concentration becoming the sourceof power of MCC.Zenith and low level convergence,high level divergence,ascending motion,and plentiful vapor contributed to the generation and development of MCC.