Abstract: The processes of the retreat of the West Pacific subtropical high from the mainland of China during Aug. 4-12, 1958 have been analysed. It is shown that the retreat first occurs in the layer of 200-400 mb and then propogates upwards and downwards, where-as, maximum changes occur at the 200 mb Ievel. However, the contour fields below 500 mb suffer small change. This situation is related to the dynamical factors near the tropopause. It is also pointed out that the retreat of the subtropical high may be largely caused by the marked changes of the meridional circulation and the easterly jet-stream which are produced by the development of the large circulation pattern. Further analysis is made on the physical mechanism of the retreat of the easterly jet-stream, the characteristic of the evolution in the structure of the high and the effect of the evolution on the retreat of the high.