Abstract: This experiment studied the ultrastructural change of histamine on LLC in C(57)BL/6J mice. There were no effects on the ultrastructure of the low dosage group. On the contrary, the high dosage of histamine had significant change showed as follows:The ratio of necleus/cytoplasm reduced and the number of nucleolus decreased, Heterochromation increased. The results indicated that histamine could induce reverse differenation which might be the function that histarnine inhibit the growth of LLC.