The work aims to tell the story behind the museum's cultural relics through storytelling design, trigger the user's situational experience and emotional resonance, and enhance the cultural experience of the digital museum. Based on the theories and methods of narratology, research methods such as literature research and logical argumentation were used to analyze the internal relationship between users, museum cultural relics resources and narrative design, and establish a character substitution narrative design model, and carry out the design practice with the Museum of the Nanyue King of the Western Han Dynasty as a case. The role substitution narrative design focused on museum cultural relics to determine the narrative theme. Visual elements and multiple forms of content were used to build a narrative space, allowing users to lead the storyline design through interface interaction, thereby establishing users’ in-depth perception of cultural situations. The role substitution narrative design can enhance the cultural experience of digital museums from the user's perceptual and emotional levels. The role substitution narrative design can realize the expansion of the perception depth and participation validity of the digital museum cultural experience. Its core is the insight and satisfaction of the user's sensory cognition and emotional experience. It provides a reference for the development and optimization of the current digital museum.