The normal value of the CT value of the lungs is a range interval, which is an average value with a numerical unit of Hu, generally negative 886 ± 22 Hu at the end of deep inhalation and negative 699 ± 52 Hu at the end of deep exhalation in the human body. The so-called CT value is generally an important reference data on CT imaging. Its principle is through the different tissues and organs in the human body after absorbing X-ray, after the attenuation coefficient converted to a numerical value, generally represents the human body tissues or organs to absorb the X-ray value of the changes in the general and the density and characteristics of the tracheal tissue is related to the general human tissues and organs of the CT value of the changes in the range of minus 1000 ~ plus 1000. When the CT value of lung tissue is found not within the normal range, it is recommended to consult a doctor as soon as possible, so that the professional doctor can find out the reason and give treatment in time.