Reverse vertical circulations often exist in shallow lakes. In order to investigate the shear rules of the vertical circulation in Taihu Lake, field observations were conducted in Meiliang Bay for nine days using an acoustic Doppler velocimeter(ADV), an acoustic Doppler current profiler(ADP), and anemometers. The shear probabilities at different water depths, which were affected by different wind directions, wind speeds, and continued wind fields with the same direction, were analyzed based on the statistics of synchronous and high-frequency data of wind-driven currents. The characteristics of the vertical profile distribution of the flow field were also studied. The results show that, when the wind moved in the ESE, ES, and E directions at a speed ranging from 2 to 5 m/s and the wind fields moving in the same direction were active for 10 to 11 hours in Meiliang Bay in May, the flow field could be stable with the highest shear rate. The shear rate was lowest with the value of 20% in the surface layer(50 cm below the water surface), and highest when it had a value of 60% in the bottom layer(7 cm above the lakebed). The inflection point, where the flow direction changed, appeared between the surface layer and middle layer, i. e. , 50 to 100 cm below the water surface. The occurrence frequencies of wind speed and wind direction, as well as the duration of wind fields with the same direction determined the reverse probability of the flow field, which determined the location of the inflection point.