Motion graphics, in contrast to traditional two-dimensional media, provide the user with an experience that is more intuitive, dynamic, multi-dimensional, rhythmic and narrative. This study examines the principles and evolution of motion graphics in digital media, including television commercials, websites, applications, interactive installations, and graphic design. By analysing their dynamic, rhythmic and narrative characteristics, this paper outlines the principles of art construction from the perspectives of time, space, communication and synthesis. It also explores the artistic expression of motion graphics through three main avenues: enhancing information presentation, expanding graphic creativity, and integrating multiple forms. To illustrate how these principles enhance information presentation, expand creative boundaries and integrate multiple forms, an in-depth literature review and a series of case studies are conducted. Conclusions focus on providing guiding principles for using motion graphics in modern digital environments.