The invention discloses an NtQPT2 gene mutant capable of reducing the nicotine content of tobacco leaves, which is characterized in that the nucleotide sequence of the NtQPT2 gene mutant capable of reducing the nicotine content of tobacco leaves is shown as SEQ ID NO: 3, and compared with an NtQPT2 gene with the nucleotide sequence shown as SEQ ID NO: 1, the NtQPT2 gene mutant capable of reducing nicotine content of tobacco leaves has c.229-230insA mutation. The mutation enables an NtQPT2 gene coding protein sequence to be changed behind a mutation site, and a truncated mutant amino acid is formed. Through systematic research, the NtQPT2 gene mutant for reducing the nicotine content of the tobacco leaves is provided for the first time, the nicotine content of the tobacco leaves of a tobacco plant obtained by the NtQPT2 gene mutant for reducing the nicotine content of the tobacco leaves is reduced by 88% compared with that of a control group, and the nicotine content of the tobacco leaves is remarkably reduced.