Background Peptide nucleic acid (PNA) has many characteristics useful in molecular biology. This paper described an effective way to raise the cell ingestion rate of PNA so as to kill gastric cancer cells. Methods Heteroduplexes of PNAs and oligonucleotides, wrapped by Lipofectamine 2000, were used to infect SGC7901 cells. The inhibitive effect of heteroduplexes was evaluated by analyzing cell clone forming and cell growth rate. Telomerase activity of SGC7901 cells was detected by polymerase chain reaction enzyme-linked immunosorbent assay (PCR-ELISA) and silver staining assay. Results PNAs showed a dose-dependent inhibition of cell proliferation. The percentage of proliferation inhibition was 99.4% after 7 days; the rate of cloning inhibition was 98. 2% after 8 days; whereas for oligonucleotide groups, at the same concentration, the percentages were 50. 1% and 67. 5% respectively. Antisense PNA-DNA-Lipofectamine 2000 group (AP-D-L group) exhibited significantly different percentages from the control groups ( P < 0.05). The test result indicated that telomerase activity of the AP-D-L group was inhibited ( P < 0.05). At the same time, the impact on cell morphology was observed. Conclusions The results showed that PNAs are potent antisense reagents. The telomeraseassociated therapies are very premising for the treatment of malignant tumours.