The three-dimensional wind fields of the heavy rain on September 19th,2005,in middle Shandong Province are retrieved and explored with ground-based dual-Doppler radar data and conventional observations.Results show that the heavy rain is caused by the cumulus-stratus mixed cloud with the shear and convergence lines in the low level.Development of the small-scale convective cell is induced by the mesoscale structure of wind field,and the cells nested in the large stratus are organized to echo bands.Along with cold air diffusing southeastward,the mesoscale structure of wind field mainly locates in the layer below 4 km.Kinetic factors of the cell with a strong echo are shear lines in the low and middle levels and cold air diffusion.Moreover,it is found that the marked vertical motion happens in the strong echo area.The wind mesoscale structure plays an important role in initiating and maintaining the heavy rain.