The methylation levels of LINE-1 and O6-methylguanine-DNA methyltransferase (MGMT) in PAHs exposure group and control group were detected by pyrosequencing (PSQ) technology, and the results demonstrated that PAHs induced LINE-1 hypomethylation, and genome-wide hypomethylation might promote genomic instability, eventually contributed tumor progression; MGMT promoter hypomethylation resulted in the abnormal expression in gene level, which reduced its ability to repair damaged genes, further exacerbating the stability of the chromosomes. This evidence concerns the gene MGMT and neoplasm.