This study was carried out to investigate the effect of water-soluble polysaccharides extract of algae Ulva rigida (WPU) on the activity of digestive enzymes and biochemical parameters of shrimp (Litopenaeus vannamei). Three replicate groups of shrimp (1.0±0.1g) were fed by four diets containing included, 0 or control, 0.5, 1 and 1.5 g/kg of WPU for 60 days. The results of this study showed that WPU was effective on the activity of digestive enzymes of L. vannamei. The best the activity of digestive enzymes were observed in shrimp that fed with 1.5 g/kg of WPU diet. Regarding biochemical parameters, the diets supplemented with three levels of WPU reduced glucose, cholesterol, triglyceride, aspartat aminotransferase, alanin aminotransferase and alkaline phosphatase in experimental shrimps. Also, protein and globulin levels of shrimp receiving WPU at 1.0 and 1.5 level were significantly higher than those fed control treatment. In conclusion, the incorporation of water-soluble polysaccharides from green algae U. rigidaat 1.5 g/kg doses improves function of digestive enzymes, carbohydrate and lipid metabolisms and nonspecific immunity in shrimp L. vannamei.