Since the early 20th century, formal composition has been widely applied in interior design education and integrated into design art. With the developing of art, formal composition has laid its own theoretical basis by referring to some basic theories. At end of the 20th century when the policy of reform and opening up was carried out in an all-around way, with the rapid increasing of the livelihood, people’s passion to pursuit material happiness was replaced by passion to spirit richness. Since then more and more people focus on the developing and applying of soft environment. In order to meet people’s demand, designers apply notions and principles of design composition to interior soft environment, not just to interior functional design, so that not only creating an innovative living environment and the spacial culture but also improving ecological environment. This paper mainly studies formal composition’s application in interior design.