The imagery of silhouette is widely used in our culture as frequently seen in picture books or sign. It seems to us closely familiar and yet remotely strange. Its form, though concise, is far from easy to explicate. This article seeks to decode silhouette through semiotic theory with examples to explore how the visual experience of objective shadow and the form of silhouette in sign and the real world create meaning and analyze its coding. By so doing, the semiotic meaning of silhouette can be clarified and to be applied as a visual language.