The paper aims to explore the application method and innovative design strategy of image narrative theory in the creation process of public welfare posters, match the image narrative characteristics of COVID-19 theme with the psychological needs of the audience, and effectively enhance the cultural value of poster communication. By analyzing the basic characteristics of public welfare poster design under the image narrative theory, combining COVID-19 narrative theme, with the model 5W1H analysis element and the narrative space, from the visual thinking audience aesthetic characteristics and psychological demands, the imagery theory and the method of graphically creative are used to transform graphic symbol of posters theme into visual language. From the perspective of image narrative and the emotional demands of the audience, the design practice is carried out, and the vertical thinking of poster design process is constructed from the three levels of audience cognition, perception and reflection, so that the multi-dimensional context and cultural value of public welfare posters can be deeply spread. The involvement of image narrative theory in the creation of public welfare posters can enrich the semantic expression of posters, further strengthen emotional communication with the audience, and effectively improve the visual expression, guiding function, and value transmission of public welfare posters. At the same time, it can enrich the single rule of formal beauty, which can not meet the emotional needs of the audience and complex design process, and provide reference ideas for the redesign of public welfare posters.