BACKGROUND There is still disadvantage in animal model for lung cancer study, no matter what is xenograft nude mice or rats/mice lung neoplasm induced by carcinogenesis.The purpose of the current investigation is to explore a simple and convenient and reliable method for lung neoplasm animal model. METHODS The prepared 36 female Sprague Dawley (SD) rats, with the range from 180 to 220g of body weight, were randomly divided into two groups, each group included 18 rats. In the study group, the rats were given 2mg of 3, 4-benzopyrene soluting in 0.2mL corn oil every two-weekly pulmonary injection for 4 times through right middle-chest percutaneous puncture under control of anaesthesia by pentobarbital sodium i.p. The controls were only given 0.2mL corn oil injection simultaneously. The rats were sacrificed after suffering from dyspnea, and the survived rats were sacrificed at narcotism in 1 year after the first 3, 4-benzopyrene toxicosis. Lung, brain, liver, esophagus and stomach of all rates were anatomized in search of tumor. RESULTS No lung neoplasm was found in the control group within 1-year observation. The earliest dyspnea caused by lung malignant neoplasm was observed in 16 week after the first injection in a rat treated with 3, 4-benzopyrene oil, then 10 rats were sacrificed and found with malignant neoplasm in theirs right lung when the rats suffered from dyspnea, and 1 rat was found a huge tumour in its right lower limb in 26 weeks after treatment. The other 6 rats were sacrificed in 1 year after the first 3, 4-benzopyrene oil treatment, in which 1 rat was found with a malignant neoplasm in its right lung and 5 rats were normal. No tumor was found in brain, liver, esophagus and stomach. Out of these 18 rats, 12 (66.67%) lung malignant neoplasms and 1 limb malignant neoplasm were found within 1 year in the experimental group which yielded a total cancerogenic rate of 72.22% (13/18). The lung neoplasms included: 2 poor-differentitaed squamous cell carcinomas, 3 adenocarcinomas and 7 undifferentiated carcinomas. CONCLUSIONS The results suggest that 3,4-benzopyrene pulmonary injection by percutaneous puncture may provide an efficiency method for lung neoplasm model established in rats.