Abstract: Chitosan is a kind of crude polysaccharid with cation in the nature, it has vast biologic function .This test was conducted to evaluat the effects of weight gain rate ,immunity on mice of two kinds of chitosan.The results showed that the intake and daily gain of mice in every group was not significant（P>0.05）; The highest dosage of two kinds of chitosan extremly imprument the T lymphocyte persentage in blood of mice(P<0.01) ,they are also higher than the other groups mice of taking chitosan (P<0.05); The second,third,fifth,sixth groups’α and content of bacteriolysin were extremely higher than contrast group(P<0.01);The effect between two kinds of chitosan on K were terribely notable(P<0.01),the effect on content of bacteriolysin of the first kind of chitosan was higher than the second one(P<0.05),still;The two kinds of chitosan had defend effect on the ratio of the mice infected by coliform,but the first kind chitosan was better than the second one.

Key words: chitosan; rats; weight gain; immunity