Abstract: In this paper , the monsoon trough in South China for ten years ( 1971-1980 ) are examined" and analysed. According to analysis, the monsoon trough are divided into two groups, one is in the land , this kind of monsoon trough occures on the border between the winter and the summer monsoons It is an important weather system during the previous rainy season in South China. The other is over the South China Sea and is related with ITCZ and monsoon trough over the Bay of Bengal. Its occurrence is not too frequent but it has serious influence on the area of South China.