Objective To investigate the reversal effect of antisense phosphorothioate oligonucleotide （ASOND) on human hepatoma resistant cells. Methods Human hepatoma resistant cells SMMC-7721 was transfected with synthetic antisense phosphorothioate oligonucleotide complementary to the 5′ region flanking the AUG initiation codon mediated by lipofectamine. In vitro drug sensitivity was measured by MTT assay. The expression of P-170 was determined by flow cytometry and mRNA was assessed by RT-PCR. Results ASOND inhibited the expression of mRNA and p-170 in SMMC-7721, enhanced the sensitivity of SMMC-7721 to chemotherapeutic drug. The best inhibitory effect was achived by the dose of 0.5μmol/L. Conclusion ASOND enhanced the sensitivity of SMMC-7721 to chemotherapeutic drug and reversed the multidrug resistance of SMMC-7721 partially.