Background: To investigate the maximum distance from lesions to the single-isocenter that can ensure the accuracy of dose delivery for single-isocenter/two-lesions intensity modulated radiotherapy (IMRT) lung stereotactic body radiation therapy (SBRT). Materials and Methods: We employed a lung phantom made of acrylic material. Sixteen gross tumor volumes (GTVs) of the same shape and size were delineated on the CT images. The single-isocenter was placed on the center of the first GTV (GTV1). Six GTV centers were located at left and were 2-7 cm away from the single-isocenter. Nine GTV centers were in the 45° direction and were 2-10 cm away from the single-isocenter. Plans were created for the first planning target volume (PTV1) and other fifteen PTVs separately with the same isocenter. Compass was used to verify the treatment plans. γ analysis was carried out with criteria of 2% / 2 mm. The passing rate shall over than 90%. If the passing rate of γ analysis was lower than 90%, two-isocenter plan was created and carried out γ analysis as well. Results: According to the γ analysis, when the distance from lesions to the single-isocenter was more than 6cm, both in the horizontal or 45° direction, the passing rate was lower than 90%. Based on γ analysis, two-isocenter plans were created. After verification, the passing rate was higher than 90%. Conclusions: The maximum distance of using single-isocenter to treat multiple lung lesions is 5 cm. The result provides a reference for our center and other centers when using this technique to treat multiple lung lesions.