Abstract: Weather Research and Forecasting(WRF) model numerical simulations were used to study the impact of vertical wind shear-including the entire, low-level, and mid-level shear-on mesoscale convective systems.The initial background field of the WRF idealized simulation was the observed radiosonde data in China that produced severe convective systems.The results demonstrated that the simulations of changing vertical wind shear in the entire layer had the greatest impact on the intensity and organizational mode of mesoscale convective systems.For increasing(decreasing) vertical wind shear, the intensity of convection increased(decreased) and the convective systems organized into convective line(decentralized).The mechanisms involved were explored by analyzing the three-dimensional characteristics of vertical velocity, horizontal wind, divergence, and the cold pool, and can be summarized in the following three aspects:(1) The interference between ascending and descending motion weakened as stronger vertical wind shear increased, which led to a longer maintenance and enhancement of vertical velocity.(2) The horizontal vorticity increased with stronger vertical wind shear, and then vertical vorticity increased(decreased) at the ascending(descending) motion under the tilting term in the vorticity equation, which led to intensification of the ascending and descending motion, respectively.(3) The intensity and height of the cold pool increased with stronger vertical wind shear, which led to linear organization of mesoscale convective systems.Other results included the fact that the near-surface wind speed and precipitation amount increased with increased vertical wind shear, and heavy precipitation appeared after the strongest wind.Strong descending motion led to strong surface wind because of the noninterference between ascending and descending motion in the development stage of the mesoscale convective system.During the mature stage, rainwater accumulated because of the constant reinforcement or maintenance of ascending motion leading to heavy rainfall.