Abstract: In order to probe that chitosan and probiotics may regulate immune function of allogynogenetic silver crucian carp (Carassius auratus gibelio) by the pathway of triiodothyroxine (T₃), tetraiodothyroxine (T₄) and cortisol in fish, allogynogenetic silver crucian carp（initial weight of 78.31±2.15 g） were fed with control and tested diets which were control diet with 0.50% chitosan A，0.50% chitosan B, 0.20% probiotics， the complex of 0.50% chitosan A and 0.05% probiotics respectively. The number, differential count and phagocytic activity of peripheral blood leucocyte, lysozyme activities in spleen, lymphocyte proliferation in spleen were measured after 64 d feeding period. The T₃, T₄, cortisol levels in serum were assessed by means of radio-immunoassay. Results showed that the supplement with chitosan, probiotics, or the complex of chitosan and probiotics had no notable influence on the number of peripheral blood leucocyte (P>0.05), but it could enhance the lymphocyte count，phagocytic percentage, phagocytic index and lysozyme activity in spleen (P<0.05), and decrease the polymorphocyte count remarkably (P<0.05). The supplement with chitosan, probiotics, or the complex of chitosan and probiotics had no notable influence on transformation of lymphocyte in spleen (P>0.05) but the supplement with 0.5% chitosan A could increase transformation of B lymphocyte in spleen (P<0.05). The supplement with chitosan, probiotics, or the complex of chitosan and probiotics could increase the serum T₃ level (P<0.05) and decrease the serum cortisol and the serum T₄ remarkably (P<0.05) except that the supplement with 0.50% chitosan B had no notable influence on the amount of T₄ (P>0.05). Thus it can be seen that chitosan and probiotics might regulate immune function of allogynogenetic silver crucian carp by the pathway of increase in serum T₃ and decrease in serum cortisol.