Data of nuclear families of 194 male proband with lung cancer and 176 controls were analyzed to study its genetic etiology in Xuanwei County of Yunnan Province. Results showed risk of lung cancer in the relatives (parents and siblings) of the proband was 1.78 times as of controls, with a statistically significant difference, and risks in parents and female relatives of the proband were 2.90 and 2.43 times as in controls, respectively, both with a statistically significant difference. Heritability of male lung cancer was 24.68%. It indicated genetic susceptibility to lung cancer in females was higher than that in males and played an important role in the etiology of lung cancer.