Abstract Blood orange is named for its blood-red flesh color. The color of blood orange flesh depends on the content of anthocyanin. The content is easily affected by temperature, light, air humidity, pH and other factors and changes. This article discusses the “redness” of blood oranges from three aspects: the formation of “red” flesh, the degree of “redness” and the impact of blood oranges on human health. It is hoped that readers will experience the chemical knowledge contained in the blood orange and feel the close connection between chemistry and life.