Yessotoxin(YTX) and its analogues are disulfated polyether compounds which have been concerned more in seafood quality monitoring and shellfish industries recently. Many studies on the toxicity of YTXs had been carried out, but the results showed apparent discrepancies. Just these discrepancies have encouraged many researchers to study the mechanism by which YTX exerts its action, such as what the target tissues are, what the pattern of the mode and precise mechanism of action are. However, the process still remains largely unclear. This paper aims to study the toxicity of yessotoxin and analyze the possible action mechanism to the nerve tissue by using histological and immunohistochemical methods. 24 hrs after tail intravenous injection with yessotoxin, the female ICR mice were killed and cerebella tissue was fixed and sliced. Hematoxylineosin（HE）staining used to study the effects of yessotoxin on nerve cells shows obvious morphological changes of Purkinji cells in cerebella tissue, such as shrinkage, deep staining of cytoplasm, nonmottled Nissl’s body and so on. According to the immunohistochemical staining of calcium binding protein S₁₀₀, there is a more positive response to YTX in test group than in control group. It seems that YTX induces the increase of Ca²⁺ concentration in Purkinji cells of mice cerebellum; it is identical to the results of other researches. To our knowledge, this is the first report of the toxicity of YTX on nervous system in China, but the work is preliminary and further studies are needed, such as the relationship between the action mechanism of YTX and Ca²⁺ signal transduction.