To assess the effect of respiratory movement on dose distribution via intensity-modulated radiotherapy (IMRT) in patients with lung cancer based on real respiratory movement parameters. Twenty-seven patients with lung cancer who underwent four-dimensional computed tomography (4DCT) and received IMRT were analyzed retrospectively to determine the three-dimensional tumor motion amplitude and respiratory period. Based on the above movement parameters, the dose distribution of the tumor on the respiratory movement platform in the head-foot and left-right directions was measured. The difference in IMRT dose distribution between the respiratory motion and static states was compared using the two-dimensional gamma analysis method, and the effect of respiratory motion on dose verification was analyzed. The mean respiratory motion period of patients was 3.3 s, and the mean tumor motion amplitude in the head-foot direction (5.6 mm) was greater than that in the left-right direction (2.1 mm) and the anterior-posterior direction (2.3 mm), with the maximum at 18 mm. The γ-passage rate tended to decrease gradually with the increase intumor motion amplitude. When the tumor motion amplitude was greater than 3 mm, the γ passage rate was less than 95% in most beams. The differences of γ-passage rates grouped by the median respiratory period were statistically significant in the left-right directional motion state. IMRT dose validation in lung canceris affected by the amplitude of tumor motion and the respiratory motion cycle. Respiratory motion management techniques are recommended for patients with a large respiratory motion amplitude to improve the accuracy of dose delivery to the target.