〔Abstract〕 Objective To investigate the expression and effects of PHD finger-like domain-containing protein 5 A(PHF5 A) in gastric cancer cells and to explore its mechanism. Methods QPT-PCR and Western blot were used to detect the expression levels of PHF5 A mRNA and protein in normal gastric cancer cell line GES-1 and gastric cancer cell lines MKN45,MGC803 and AGS. MGC803 cells transfected with negative control empty lentivirus were used as the control group. Two knockdown groups which were transfected with two different interfering sequences lentivirus against the PHF5 A gene were used as the experimental groups. The proliferation ability was observed by cell proliferation curves and colony formation assay. The migration ability was observed by wound healing assay. Western blot was used to detect the expression levels of some signaling molecules such as Transcription factor p65(NF-κB p65), NF-kappa-B inhibitor alpha(Iκbα), p-Iκbα and Cyclin-D1-binding protein(Cyclin D1) in NF-κB signal transduction pathway. Result The expression levels of PHF5 A mRNA and protein in gastric cancer cells were significantly higher than those in normal gastric mucosal epithelial cells. After knockdown the expression of PHF5 A gene, the level of PHF5 A protein decreased. Compared with the control group, the proliferation, migration and colony formation ability of MGC803 cells in two PHF5 A knockdown groups sh1 and sh2 decreased obviously. At the same time, the result of western blot showed that the expression of NF-κB,p-IκBα,Cyclin D1 significantly decreased in experiment groups(P<0.05). Conclusion PHF5 A is highly expressed in gastric cancer cells. Lentivirus-mediated inhibition of PHF5 A gene expression can reduce the proliferation and migration ability of MGC803 cells. The mechanism may be related to the inhibition of NF-κB signaling pathway.