Three stocking densities from 300 ind/m³ to 900 ind/m³ were applied under the conditions of non-drug use, adding probiotics and zero water exchange during the construction of nitrifying biofloc system, and the effects of stocking densities on water quality and growth of Litopenaeus vannamei and the suitable density of culture were analysed by ninety day period of indoor seawater culture. The results show that:In the process of constructing nitrifying biofloc system, the water quality of gradually declined with increasing density. For example, the DO of the BFT900 group dropped from 8.21 mg/L to 3.34 mg/L, pH from 8.24 to 6.75, TAN rose from 0.08 mg/L to 1.64 mg/L, NO₂^--N from 0.10 mg/L to 10.80 mg/L, NO₃^--N from 0.54 to 153.70, rose the differences of the above indexes in each group were significant(P<0.05). After the transformation of nitrifying biofloc system was successful, the water quality indexes of each group were in the suitable range for shrimp growth; The survival rate decreased with increasing density. The survival rates of the three treatment groups (BFT300, BFT600 and BFT900) were 84.59%±8.83%, 74.26%±6.66% and 54.95%±4.23% respectively, and there was a significant difference among the three groups(P<0.05); At the end of culture, the average length and weight of shrimp decreased with increasing density. The average length and weight of shrimp in group BFT300 were significantly higher than those in groups BFT600 and BFT900(P<0.05); The highest yield of BFT600 groups was (5.45±0.48) kg/m³, but there was no significant difference with group BFT900 (P>0.05), but the yield was significantly higher than that in group BFT300[(4.08 + 0.63) kg/m³], and the feed coefficient rate increased with the increase of density, and there was no significant difference between BFT300 and BFT600 groups(P>0.05), but they were significantly lower than those in group BFT900 (1.82 + 0.62)(P<0.05). According to the comprehensive effects of culture and the benefit of production, 300-600 ind/m³ could be the reference density range for Litopenaeus vannamei indoor seawater culture based on practical situation during the construction of nitrifying biofloc system.