A severe convective weather with hail and strong winds accompanied by the squall line process occurred in Nantong, Jiangsu Province on 30 April 2021. The WRF-ARW model was used to conduct sensitivity numerical experiments to investigate how the environmental field influences the evolution of the convective system. Results indicate that the strong winds weather was closely related to the structure and intensity of the squall line system. The intensity of the cold pool in the squall line affected the formation and intensity of the strong winds. The corresponding dynamic and thermal forces combined affect the intensity of the downdraft, thus affecting the surface wind speed. The intensity and range of the cold pool were weakened by the increase of middle-level water vapor, the squall line intensity was weakened and the moving speed was slow. When the raindrop evaporation was turned off, the resulting convective system had no cold pool, and its structure was different from the squall line. The weakening or disappearance of the cold pool weakens the downdraft, weakens the divergence in the lower layer, and the momentum in the middle layer cannot be transmitted downward, leading to the weakening of the surface wind speed.