Abstract: In the previous study， the numerical simulation or meteorological satellite data were wildly used for the analysis on the precipitation system in the monsoon trough， however， the dual-polarization radar were few used. In the report， based on the tropical disturbance precipitation system caused by South China Sea monsoon trough near Yongxing Island （Oct. 17， 2021）， combined with S-band dual-polarization radar and ground automatic precipitation observations， the application study on dual-polarization radar was performed. The results showed that the typical case is mainly affected by the monsoon trough in the South China Sea， the wind field has obvious convergence phenomenon with abundant water vapor， and the subtropical belt extend westward； the process can be divided into three stages， in which the convective properties dominate in the second and third stage of the mixed cloud system. From 10：00 to 11：00， the vertical liquid water content and radar echo top of the mixed cloud system increases suddenly， and there are weak “Z _DR column” phenomenon observed when the small parts of the cloud system were above 5 km； From 11：00 to 12：00， the areas exceeding 50 dBZ are mainly concentrated below 6 km， the areas whose differential reflectivity （Z _DR） more than 1dB are significantly larger than that of the other stages， and the correlation coefficients （CC） are basically maintained in the range of 0.9-1.