Abstract: Light quality can influence the photosynthetic characteristics, morphology and physiological processes of seedlings. We studied the effects of different light qualities(white light, W; red light, R; blue light, B; a mixture of red and blue light, RB) using light emitting diodes(LEDs) on growth, morphology and photosynthesis of mulberry(Morus alba L. cv. Longsang No. 1) seedlings. The results showed that compared with seedlings grown under W, the dry matter accumulation of seedlings grown under R, B and RB was inhibited. The stem length and leaf area of seedlings grown under R were significantly larger than that of seedlings grown under W, RB and B. However, the leaf mass per area(LMA), chlorophyll a/b ratio, soluble protein content, sucrose and starch content, and total leaf nitrogen(N) content of seedlings grown under W, RB and B were significantly higher than that of seedlings grown under R. The net photosynthetic rate(P_n), stomatal conductance(G_s), and the actual photochemical efficiency of PSⅡ(ΦPSⅡ) of seedlings grown under RB treatment were similar to that of seedlings grown under W treatment, and the P_n and ΦPSⅡ of seedlings grown under R and B were lower than those of seedlings grown under W and RB. Antioxidant enzyme activity of seedlings grown under R, RB and B was higher than that of seedlings grown under W, yet the malondialdehyde(MDA) content of seedlings grown under R, RB and B was lower than that of seedlings grown under W. The number of leaf stomata on mulberry leaves grown under B was greater than all other treatments, and R-grown seedlings had the fewest stomata. Light quality also changed the leaf anatomical structure of mulberry seedlings. The leaf thickness, palisade tissue length and spongy tissue length of seedlings grown under R treatment significantly decreased. Hence, this study indicates that a certain ratio of mixed red and blue LEDs light could change the growth, photosynthetic characteristics, physiological characteristics, and leaf anatomy of mulberry seedlins, just like those of W-grown seedlings. Additionally, the mixed red and blue LEDs light reduced the adverse effects of monochromatic red and blue LEDs light on plant growth and development.