Objective To explore the role of RegⅠ（ regenerating gene I） in the pathway of gastrin stimulating proliferation of gastric cancer cells. Methods According to mRNA sequence of RegⅠ gene in Genbank, three siRNAs specifically targeting RegⅠ gene were designed through online design and homology comparison, and the RegⅠ-shRNA vectors(pSUPER-EGFP-REG/1, pSUPER-EGFP-REG/2 and pSUPER-EGFP-REG/3)were constructed. The three reconstructed vectors were identified by Hind Ⅲ/ EcoR Ⅰ double-enzyme digestion and DNA sequencing. Gastric cancer cells BGC823 and SGC7901were transfected with three RegⅠ-shRNA vectors respectively. The experimental control group was transfected with pSUPER-EGFP-I whereas the contol group was no plasmid transfect. The cells were transfected with lipofectamine TM 2000 transfaction reagent and screened with RPMI-1640 supplement with G418 The gastric cancer cell lines BGC-823 and SGC-7901 with knock-down RegⅠ gene were estabilished by detection of RegⅠ mRNA level with RT-PCR, and protein expression was measured by Western boltting.Effect of gastrin on stimulating proliferation of gastric cancer cells was measured by MTT assay. Results The results of Hind Ⅲ/EcoRⅠ restriction map and sequencing of inserted sequence were correct, and indicated that three RegⅠ-shRNA expression vectors were constructed successfully. RT-PCR results indicated that RegⅠ mRNA transcription in gastric cancer cell BGC823 and SGC7901 were inhibited effectively by pSUPER-EGFP-REG/1 Western boltting results showed that compared to empty-vector, RegⅠ protein was down-regulated to （45±4）% and（53±4）% in BGC823 and SGC7901 cells, respectively. MTT results showed that the proliferation efficiency in the gastric cancer cell line with knock-down as RegⅠ gene as decreased significantly (EM>P /EM>0.05). The gastric cancer cell lines BGC823 and SGC7901 was knock-down as RegⅠ gene was incubated with gastric G17 at the most effective concentration and time.MTT assay was used to detect the proliferative changes of gastric cancer cell.After incubation with gastrin,t