Background and Objectives: Placental Growth Factor (PlGF) is a member of Vascular Endothelial Growth Factors (VEGF) family, which can directly act on angiogenesis, tumor cells motility, tumor metastasis, growth and tumor survival. The purpose of this study was to investigate the preventive effect of siRNA on PlGF gene in gastric cancer cells. Materials and Methods: In this experimental study, gastric adenocarcinoma cells (AGS) with 40 picomol concentration of small interfering RNA (siRNA) related to PlGF gene and cellular migration test was carried out, using wound healing model. Results: PlGF gene 24 and 48 hours after of treatment, expression inhibition showed that migration of AGS cells was prevented compared with control condition, but in 72 hours’ time interval, treatment samples showed migration reduction more than control sample. Conclusion: According to these results, reduction of PlGF gene expression may prevents AGS cells migration and metastasis.