Abstract: Objective To investigate the relationship of the expression transformation of claudin-1 with the invasiveness and metastasis in the gastric carcinoma. Methods By using the immunohistochemistry, the expression of claudin-1 in areas of mueosa and invasive front of 136 gastric adeocarcinomas. Results In the areas of mucosa, it is found that the relationship of the claudin-1 high-expression rate with the degree of differentiation is negative,however, the its relationship with invasiveness and metastasis is positive in the gastric carcinoma. In the areas of the invasive front, the relationship of the claudin-1 high-expression rate with the differentiation and invasiveness and metastasis of the gastric carcinoma is posive, in which the expression of claudin-1 transformed from low to high. The deeper the invasiveness, the higher the transformation. The claudin-1 expression transformation rate in the patients with metastasis was higher than those with not metastasis. Conclusion The up-regulation of claudin-1 expression and the expression transformation with the invasiveness and metastasis in the gastric carcinoma suggested that the claudin-1 participated in the transformation of biological behaviour in neoplasms, however, the precise mechanism and the relationship of the claudin-1 expression with the neoplasm progress need further study.