OBJECTIVE： To extract and identify the volatile oil from the flowers of Citrus grandis， and evaluate inhibitory effects of it on the proliferation and migration of lung cancer A549 cells in vitro. METHODS： The volatile oil was extracted from the flowers of C. grandis by steam distillation. The chemical constituents were analyzed by GC-MS. Relative percentage of each component was calculated by peak area normalization. Inhibitory effect of volatile oil on the proliferation of lung cancer A549 cells was detected by MTT assay， and the relative activity and proliferation inhibitory rate were calculated. Inhibitory effect of volatile oil on the migration of lung cancer A549 cells was evaluated by cell scratch test， and the relative migration area and migration inhibitory rate were calculated. RESULTS： Totally 0.7 g volatile oil was obtained from 100 g flowers of C. grandis with a yield of 0.7％. A total of 46 chemical components were isolated from the volatile oil， among which there were 35 compounds identified， accounting for 96.95％ of the total peak area. The compounds with relatively higher percentage content included D-limonene （28.43％）， γ-terpinene （20.74％）， β-myrcene （11.97％） and linalool （7.41％）， etc. Compared with blank control group， 120 mg/L volatile oil from the flowers of C. grandis could significantly reduce the relative activity of lung cancer A549 cells （P＜0.05）， and the proliferation inhibitory rate increased to 21.72％. The volatile oil from the flowers of C. grandis had no obvious inhibitory effects on the relative activity of lung cancer A549 cells at the concentration of 1， 5， 10， 20， 40， 60， 80， 100 mg/L （P＞0.05）. After treated for 24， 48 h， the volatile oil from the flowers of C. grandis could significantly reduce the relative migration area of lung cancer A549 cells at the concentration of 60， 120 mg/L （P＜0.05）； and the migration inhibitory rate were 132.46％， 125.08％ （24 h） and 124.54％， 124.66％ （48 h）， respectively. But 30 mg/L volatile oil from the flowers of C. grandis had no obvious inhibitory effects on the relative migration area of lung cancer A549 cells （P＞0.05）. CONCLUSIONS： GC-MS can be used for identifying chemical compositions of volatile oil from the flowers of C. grandis. Volatile oil from the flowers of C. grandis are mainly D-limonene， γ-terpinene， β-myrcene， etc.， which can inhibit the the proliferation and migration of lung cancer A549 cells.