TECHNOLOGY FOCUS - BIOLOGY - Preparation (Claimed): The preparation of (I) whose PNA is -CONH-Tn-CONH2, comprises either: (a) using dehydrated catalyst and diisopropylethylamine to activate the peptide nucleic acid monomer whose basic group is T1, reacting it with 4-methylbenzhydrylamine (MBHA) resin in the organic solvent to obtain MBHA-T1 compound, (b) performing dehydration reaction to MBHA-T1 compound and the peptide nucleic acid monomer whose basic group is T2 to obtain MBHA-T1T2 compound, (c) repeating step (b) for (n-2) times to obtain MBHA-T1T2 up to Tn compound, (d) using dehydrated catalyst and diisopropylethylamine to activate PDI, reacting it with MBHA-T1T2 up to Tn compound to obtain MBHA-T1T2 up to Tn-R1-PDI compound, (e) using dehydrated catalyst and diisopropylethylamine to activate peptide nucleic acid monomer whose basic group is A1 to obtain MBHA-T1T2 up to Tn-R1-PDI-R1-A1 compound, (f) performing dehydration reaction to MBHA-T1T2 up to Tn-R1-PDI-R1-A1 compound and peptide nucleic acid monomer whose basic group is A2 to obtain MBHA-T1T2 up to Tn-R1-PDI-R1-A1A2 compound, (g) repeating step (f) for (n-2) times to obtain MBHA-T1T2 up to Tn-R1-PDI-R1-A1A2 up to An compound, (h) using dehydrated catalyst and diisopropylethylamine to activate Pc, reacting it with MBHA-T1T2 up to Tn-R1-PDI-R1-A1A2 up to An compound to obtain MBHA-T1T2 up to Tn-R1-PDI-R1-A1A2 up to An-R2-Pc compound, (i) reacting MBHA-T1T2 up to Tn-R1-PDI-R1-A1A2 up to An-R2-Pc compound with trifluoroacetic acid and trifluoromethanesulfonic acid, using ethyl acetate to precipitate, collecting the precipitate to obtain peptide nucleic acid molecule coupled with PDI and Pc, (j) dissolving the peptide nucleic acid molecule coupled with PDI and Pc in the mixed solution formed by warer (50 mu l) and aqueous sodium chloride solution whose concentration is 200 mM/l, placing it in the culturing container for 2 hours under the temperature of 37 degrees C to obtain (I) whose PNA is -CONH-Tn-CONH2; or (A) using dehydrated catalyst and diisopropylethylamine to activate the peptide nucleic acid monomer whose basic group is T1, reacting it with MBHA resin in the organic solvent to obtain MBHA-T1 compound, (B) performing dehydration reaction to MBHA-T1 compound and the peptide nucleic acid monomer whose basic group is T2 to obtain MBHA-T1T2 compound, (C) repeating step (B) for (n-2) times to obtain MBHA-T1T2 up to Tn compound, (D) using dehydrated catalyst and diisopropylethylamine to activate Pc, reacting it with MBHA-T1T2 up to Tn compound to obtain MBHA-T1T2 up to Tn-R1-Pc compound, (E) reacting MBHA-T1T2 up to Tn-R2-Pc with trifluoroacetic acid and trifluoromethanesulfonic acid, using ethyl acetate to precipitate, collecting the precipitate to obtain peptide nucleic acid molecule A of formula (HOOC-T1T2 up to Tn-R2-Pc), (F) using dehydrated catalyst and diisopropylethylamine to activate peptide nucleic acid monomer whose basic group is A1, reacting it with MBHA resin in the organic solvent to obtain MBHA-A1 compound, (G) performing dehydration reaction to MBHA-A1 compound and peptide nucleic acid monomer whose basic group is A2 to obtain MBHA-A1A2 compound, (H) repeating step (G) for (n-2) times to obtain MBHA-A1A2 up to An compound, (I) using dehydrated catalyst and diisopropylethylamine to activate Pc, reacting it with MBHA-A1A2 up to An compound to obtain MBHA-A1A2 up to An-R2-Pc compound, (j) using dehydrated catalyst and diisopropylethylamine to activate peptide nucleic acid molecule A of formula (HOOC-T1T2 up to Tn-R2-Pc), reacting it with PDI for 10-60 minutes, adding peptide nucleic acid molecule B of formula (MBHA-A1A2 up to An-R2-Pc) to react for 10-60 minutes to obtain peptide nucleic acid coupled with PDI and Pc, (K) dissolving the peptide nucleic acid molecule coupled with PDI and Pc obtain in step (I) in the mixed solution formed by warer (50 mu l) and aqueous sodium chloride solution (50 mu l) whose concentration is 200 mM/l, placing it in the culturing container for 2 hours under the temperature of 37 degrees C to obtain the peptide nucleic acid nano-heterojunction whose PNA is -CONH-Tn-CONH2, where in the steps (a)-(h) and (A)-(H), the T1, T2 until Tn are compounds of (IIa), (IIb), (IIc), (IId), (IIf), (IIg) or (IIh), the A1, A2 until An are adenine, the dehydration catalyst is O-benzotriazole-N,N,N',N'-tetramethyluronium-hexafluorophosphate and 1-hydroxybenzotriazole, and the organic solvent is N,N-dimethylformamide and dimethyl sulfoxide. In the steps (a)-(i), where the reaction temperature is 25 degrees C, the reaction time is 10-60 minutes, preferably 20-30 minutes. In the steps (A)-(I), the reaction temperature is 25 degrees C. Preferred Components: The diameter of the peptide nucleic acid nano-heterojunction is 2-5 nm, preferably 3 nm, and the length is 1-10 nm, preferably 3-6 nm.