According to that LED(Light Emitting Diode) lighting can affect the shape of a plant, this paper proposes to use LED supplementary lighting to promote herb structure of medicinal plants. By combining optical and botanical experiments, four light sources with different spectral energy distributions, i.e., composite white LED and yellow LED, homo-light red LED and blue LED are used to provide supplementary lighting on medicinal plant Photinia, the light intensity is controlled at(200+-S)umol m-2s-1, after sun set, LED supplementary lighting is conducted for three hours every day, parameters such as area and perimeter of leaves, the plant’s medicinal part, are measured after supplementary irradiation. The results show that white and yellow LED lights can enlarge the medicinal structure of the plant, that red and blue LED can decrease the area of medicinal structure of the plant, and that red LED largely affects the shape of the plant leaves. The conclusion provides theoretical and experimental basis for LED lighting to promote medicinal structure of herb plants.