Abstract: Using regular observation data and regional automatic station rainfall data, 1°×1° NCEP 6h interval reanalysis data, sub-high index data provided by the National Climate Center, the process of continuous heavy rainstorm to severe rainstorm in northern Liuzhou from 9 to 15 August 2017 was analyzed. The results show that the continuous rainfall process can be divided into three stages: stable subtropical high and eastward movement of small plateau fluctuations, westward movement of subtropical high and northward movement of shear line, southward pressure of North China trough and eastward retreat of subtropical high.In the first stage, the middle layer dry cold air invades, the lower layer warm and wet air increases, and the layer-trough gradient increases. Heavy precipitation occurred on the south side of the front zone. During the process of strengthening the low southwest airflow, the precipitation zone was concentrated in three northern counties of Liuzhou. In the second stage, the subtropical high strengthens and extends westward, and the whole layer of Guangxi turns to the southwest jet stream. North Guangxi is near the jet axis, and there are two centers of vertical motion. Northern Guangxi is in the unstable stratificaiton of high temperature and high humidity. The middle layer is affected by the sub-high subsidence airflow, and the low-level warm and humid unstable energy is concentrated. When the near-surface ultra-low level jet is strengthened and the jet axis is pushed northward, the cyclone shear on the left side and the convergence and uplift of wind speed trigger rainstorm. In the process of unstable energy release, two vertical motion centers in the high and low layers are opened, and the upward movement is further strenghened. The southern boundary of the heavy rainfall area recieved the junction of Sanjiang area, the rain is stronger, the rainstorm is no time interval. In the third stage, the dry cold air in the middle and upper layers expands to the lower layers, where it converges with the warm and wet air in the lower layers. The southern pressure of the lower shear line enters Guangxi. The strong convergence and uplift of the low level triggers heavy rainfall. The dry intrusion of the middle and high levels has an enhanced effect on rainfall. The heavy rainfall area gradually southwards from northern Guangxi to southern Guangxi with the eastward retreat of the subtropical high, and its intensity, range and cumulative rainfall are the largest. strong convergence and uplift of the low level triggers heavy rainfall. The dry intrusion of the middle and high levels has an enhance effect on rainfall. The heavy rainfall area gradually southwards from northern Guangxi to southern Guangxi with the eastward retreat of the subtropical high, and its intensity, range and cumulative rainfall oare largest.