Objective To observe the ability of triple helix-forming oligonucleotides (TFOs) modified with manganese porphyrin to combine with and cleave HBV DNA fractions. Methods TFO were modified with manganese porphyrin and acridines, and then reacted with the 32P labeled HBV DNA fragments at 37℃ in vitro (pH 7.4). Electrophoretic mobility shift assays and Dnase Ⅰ footprinting tests were used to show the affinity and specificity of TFO to bind to target sequences. The ability of TFO to cleave HBV DNA fragments was tested by cleavage experiments. Results TFO modified with manganese porphyrin and acridine could bind to the target sequence in a sequence-dependent manner, with a Kd value of 3.5×10-7 mol/L and a relative affinity of 0.008. In the presence of potassium monopersulfate (KHSO5), TFO modified with manganese porphyrin and acridine could cleave the target sequence where the triplex DNA was formed. Conclusion In the presence of KHSO5, TFO modified with manganese porphyrin and acridine could bind and cleave the target HBV-DNA in a sequence-dependent manner.