To analyze the conception and expression path of motion graphics under the background of digital media to summarizes the design dimension, and to provide some theoretical and practical references for innovative design of motion graphics in the context of new media, the paper sorts out the design origin of motion graphics by using the literature method and the inductive summary method. Using the method of case analysis, combining with the relevant theories of design and psychology, the paper analyzes the creative idea dimension of motion graphics from the aspects of text, graphics, sound and color, etc. At the same time, the paper also discusses the innovative expression dimensions of motion graphics from the perspectives of dynamics, time, space, indirect and direct.Under the background of digital media, motion graphics make the transmission of information more vivid, intuitive and efficient, whether in visual language or in dynamic design. The digital media environment puts forward new requirements for the design of motion graphics and provides new design thinking and methods. Motion graphics will develop in a flawless direction in information experience and perception interaction.