The aim of this study was to investigate effects of lactic acid bacteria, Leuconostoc mesenteroides B4 and its dextran product, on the growth, hepatopancreatic microflora, immunity and disease resistance of white shrimp (Litopenaeus vannamei). The shrimp were fed control and diet supplemented with L. mesenteroides B4 (107CFU/g) +dextran (0.05%) for 8 weeks. The result showed that percent weight gain and feed efficiency of the shrimp fed diet supplemented with L. mesenteroides B4 + dextran were significantly higher than that of the control group (p <0.05) from the 2nd to the 8th week. When the white shrimp were fed the control group and fed diet supplemented with L. mesenteroides B4 + dextran for the 8th week, the microflora of the shrimp hepatopancreas was analyzed. Among the totalgenome , the proportion of the microflora of the shrimp hepatopancreas in the control group and the experimental group was the highest, all are Rhodobacteraceae bacterium (68.08% and 66.84%). In terms of immune index, when white shrimp was fed a feed supplemented with L. mesenteroides B4 + dextran product for 8 weeks, there was no significant difference in blood phenoloxidase activity and respiratory burst from the control group (p> 0.05). After challenge with Vibrio parahaemolyticus, survival rate of white shrimp that had L. mesenteroides B4 + dextran supplement was significantly higher (90%) than that of the control group (10%) (p<0.05) . Overall , the resultsindicated that the L. mesenteroides B4 and its product, dextran, could improve growth performance and resistance to vibriosis infection in white shrimp.