The invention discloses a tobacco NtSLAC1 gene mutant as well as a molecular identification method and application thereof. The tobacco NtSLAC1 gene mutant is Ntslaac1-1, G at the 57th site of a tobacco NtSLAC1 gene is mutated into A, a termination codon is formed, and the gene is terminated in advance; and the nucleotide sequence of the gene mutant Ntslaac1-1 is as shown in SEQ ID NO. 2. The tobacco NtSLAC1 gene mutant, the molecular identification method and the application are provided for the first time through systematic research, according to a tobacco plant obtained through the NtSLAC1 gene mutant Ntslaac1-1 for reducing the chlorine ion content in tobacco leaves, the chlorine ion content in the tobacco leaves is reduced by 51.4% compared with a control group, and the chlorine ion content in the tobacco leaves is remarkably reduced.