Objective To screen down regulated genes and find down regulated novel genes in gastric cancer. Methods Genes mRNA expression were detected between gastric cancer and normal gastric mucous membrane of five patients using cDNA microarray. Genes mRNA expression signals on hybridization membranes were analysized with computer software. Down regulated genes in gastric cancer were screened. cDNA suppression subtraction library was established by counterpart normal gastric mucous membrane mRNA(Tester) subtracting gastric cancer tissues mRNA(Driver) of five patients. After identification of the subtraction library, positive clones choosen randomly were sequenced , and down regulated novel genes in gastric cancer were screened. Some of the genes were identified by RT PCR.Results Down regulated genes in gastric cancer consist of 60 genes including tumor suppressing genes, apoptosis related genes, DNA replication and transcript or translate related genes, cell cycle related genes, cell migration related genes, etc. Two unknown gene fragments in gastric cancer were cloned. Conclusions Sixty down regulated genes in gastric cancer are confirmed. They are involved in gastric tumorigenicity and metastasis. cDNA subtraction library of gastric cancer was constructed successfully. Two down regulated novel gene fragments in gastric cancer was found.