Because of response of the surface air flow to the distinct thermodynamic and dynamic disturbances by the complex topography in Guizhou Province,the convective-stratiform mixed clouds in which several convective cells imbed occur frequently.A typical convective-stratiform mixed clouds system in Guizhou Province on 29 May 2005 is studied in detail with observation data and simulation results.Results show that the convective-stratiform mixed clouds system is formed by cumulus merging and stratification,and the formation process goes through three typical merging stages.Precipitation is widespread with inhomogeneous distribution,and several strong centers embedded in rain field,which locate in small convective cells with the maximum precipitation of 60 mm.In the formation process of convective-stratiform mixed clouds,the ultimate cause why the intense precipitation occurs is that wind field and water content experience dramatic changes by release of instability energy during this process.