Objective: Inhibition mechanism of telomerase inhibitor phosphorothioate antisense oligodeoxynucleotides (PS-ODN) on colorectal cancer cells is probed through cells culture and experimental observation of inhibition function of PS-ODN on LS-174T cells of colorectal cancer. Methods: To induce cells to die by adopting anti-sense technology to block telomerase RNA at reverse transcriptase level, and to evaluate the inhibition effect by means of cell clone forming、growth curve、electron microscope、 FCM、PCR-Elisa、etc. Results: The best dosage of PS-ODN was 10 μ mol/Ls. After ten days’ inhibition, the collective forming rate of LS-174T cells in group PS-ODN was obviously lower than that of those in group CPS-ODN and the contrast group ( P<0.01); The cells in group PS-ODN have obvious morphology change; After 72 hours’ inhibition, the cells in group PS-ODN show apoptosis peak, but this doesn’t happen in contrast group; telomerase activity of group PS-ODN was much lower than that of those in group CPS-ODN and the contrast group( P <0.01). Conclusions: Peculiar polynucleotide sequence can inhibit telomerase activity, and induce cells to wither and die. The treatment tactics of malignant tumours induced by telomerase activity is very promising.