The article investigates and analyzes water ingress problem of a certain car model at the A-pillar.It finds the water inlet point through the rain test and analyzes them from the outside part to the inside part.Finally,the design and process improvement requirements of the problem are proposed.In addition,the article summarizes the process of handling this type of water ingress problem,providing experience reference for other similar problem handling and the development of new models,and improving the overall sealing performance.