Abstract: In order to assess the effect of Yucca extract on growth performance, nutritional composition, serum immune of juveniles and aquaculture water environment, five formula feeds contained Yucca Extract at levels of 0.00% (D0), 0.05% (D1), 0.10% (D2), 0.20% (D3) and 0.40% (D4) were fed with juvenile Turbot (Scophthalmus maximus). The result showed that, no significant difference occurred in weight gain, specific growth rate, feed conversion ratio, viscerosomatic index, hepatosomatic index and condition factor of fish among all dietary treatments (P 0.05). Water, crude protein and crude lipid content of whole fish, muscle and liver exhibited no significant difference among groups (P 0.05). Serum lysozyme was enhanced in fish fed diet D3 significantly, while all immune indices were reduced in fish fed diet D4. The activities of alanine transaminase and aspartate aminotransferase of fish fed diet D3 and D4 were lower than that of the control dietary treatment (P 0.05). Except D1-6h, Ammonia content of all dietary treatments were significantly lower than that of the control treatment (P 0.05). Nitrite content of all dietary treatments were higher than that of the control treatment (P 0.05), while total nitrogen, total phosphorus and phosphate content showed no significant difference to the control treatment (P 0.05). The optimum content of Yucca Extract for juvenile turbot was 0.20% of weight based on the consideration of non-specific immunity and ammonia nitrogen content in aquaculture water.