Abstract: To investigate the biological characteristics of grass carp dendritic cells (Ctenopharyngodon idellus) and the regulatory mechanisms of dendritic cells by Bacillus subtilis, we isolated and gained grass carp dendritic cells to analyze morphological features, unique biological functions and authorized surface molecular markers. The expression of immune-related cytokines of dendritic cell to Bacillus subtilis stimulation was analyzed by RT-PCR. Our results showed that DCs have classical dendritic morphological features to initiate T cell proliferation and migration ability. LPS stimulation promoted the maturation progress of dendritic cells by increasing the expression of surface molecular markers CD83 and CD80/86, suggest that grass carp DCs were morphological and functional homology to mammalian dendritic cells. The expression of anti-inflammatory factors Il-4 and Il-10 increased significantly after the stimulation of UV-killed Bacillus subtilis (P<0.05), and reached to the highest level at 12h, revealing that Bacillus subtilis can promote the expression of anti-inflammatory factors to regulate the immune functions of dendritic cell. In conclusion, these results explored the biological characteristics of teleost fish dendritic cells and characterized the influence of probiotics Bacillus subtilis on the immune functions.