An 8-week feeding trial was conducted to evaluate the effects of different inclusion levels of Gracilaria lemaneiformis powder (G. lemaneiformis) on growth performance, hematological parameters and salinity stress tolerance test of juvenile Litopenaeus vannamei. Six formulated diets with six different levels (0%, 1%, 2%, 3%, 4%, 5%) of G. lemaneiformis were fed to triplicate groups of juvenile L. vannamei (mean initial weight 0.27±0.01g) for 8weeks. After 8weeks trial, results showed that final body weight (FBW) and weight gain (WG) of shrimp fed with 2% and 3% G. lemaneiformis diets were significantly higher than those of shrimp fed with other diets (P<0.05). Feed efficiency ratio (FCR) of shrimp fed with 3% G. lemaneiformis diets were significantly lower than that of shrimp fed with 0%, 1%, 4% and 5% G. lemaneiformis diets (P<0.05) but without significant difference with shrimp fed with 2% G. lemaneiformis diet (P>0.05). Protein efficiency ratio (PER) and muscle percent had the same trend with WG. No significant differences were found in whole body and muscle compositions (P>0.05). Hematological parameters showed that AST of shrimp fed with 2% G. lemaneiformis diet was significantly lower than that of shrimp fed with 0%, 1%, 4% and 5% G. lemaneiformis diets (P<0.05) but without significant difference with shrimp fed with 3% G. lemaneiformis diet (P>0.05); ALT of shrimp fed with 2% G. lemaneiformis diet was significantly lower than that of shrimp fed with all other diets (P<0.05). After salinity stress for 5h, survival rate of shrimp fed with 1%–5% G. lemaneiformis diets were higher than that of shrimp fed with 0% G. lemaneiformis diet, and the highest survival rate was found in shrimp fed with 2% G. lemaneiformis diet. These results indicated that G. lemaneiformis powder can improve growth performance, non-specific immune response and salinity stress resistance of juvenile L. vannamei. The WG indicated that the optimum supplement of dietary G. lemaneiformis should be 2%–3%.This study indicates that moderate levels of dietary G. lemaneiformis can significantly improve growth performance and resistance to salinity stress of L. vannamei. The results will contribute to promote the application of G. lemaneiformis in aquafeed of the white shrimp.