Abstract: A molecular marker for identifying DNA methylation and thereby detecting the benignity or malignancy of a lung nodule is disclosed. The molecular marker for identifying DNA methylation includes the sequence of, or the completely complementary sequence to, SEQ ID NO:6 or a continuous fragment of at least 55% of the full length of the sequence of, or the completely complementary sequence to, SEQ ID NO:6. Also disclosed are applications of the molecular marker for identifying DNA methylation, including a corresponding detection reagent kit and a corresponding detection method. The disclosed molecular marker combinations for identifying DNA methylation are highly correlated to lung cancer, are highly sensitive and specific when used to detect the benignity or malignancy of a lung nodule, and can increase the detection rate of malignant lung nodules while lowering the false positive rate.