DNA methylation is one of the most common forms of epigenetic modification, and it is closely related to the development of bronchial asthma, but its mechanism is unclear. Without altering the sequences of genes, DNA methylation can transfer the cytosine on the 5' end of CpG dinucleotide into methyl cytosine by DNA methyltransferase. Hence, DNA methylation can regulate gene expression, leading to the development and progression of diseases. In this review, we summarized the roles of DNA methylation in bronchial asthma, including related predisposing factors and mechanisms of action.