Objective: To screen out the genes related to peritoneal metastasis from gastric cancer, so as to provide clues to the underlying mechanisms of peritoneal metastasis of gastric cancer. Methods: The models of subcutaneously transplanted human gastric cancer in nude mice were established using SGC-7901 cell line. After three subcutaneous passages of the original xenograft through mice, the small dissected pieces of solid tumor were introduced into the stomach wall of nude mice. Tumor tissues from the original transplant sites and metastases were collected. Gene chip technology was used to determine the differentially expressed genes between the original tumor and metastasis, and then RT-PCR was performed to validate the result of the gene chip analysis. Results: Fifteen orthotopic transplant nude mice with gastric cancer were established, of which, the tumor formation rate in stomach wall was 100% (15/15) and the incidence of peritoneal metastases was 40% (6/15). There were 192 up-regulated genes and 139 down-regulated genes as shown by gene chip hybridization analysis. The highly expressed regenerating gene IV (Reg IV) was tested by RT-PCR and the result was consistent with that of the gene chip analysis. Conclusions: There are differentially expressed genes between the primary tumor and metastases of gastric cancer, some of which may possibly play an important role in peritoneal metastasis of gastric cancer.