Normal values for CT of the lungs are -886+/-22 HU at the end of deep inspiration and 699+/-52 HU at the end of deep expiration. CT, also known as computed tomography, shows the distribution of tissue density over a portion of the body’s fault line, providing a clearer image with higher density resolution and no interference from the rest of the tissue compared to traditional X-rays. During the CT examination, the subject needs to be braked, especially for chest and abdominal CT examination before scanning should pay attention to the training of breath-holding, which can eliminate the artifacts produced by respiratory movement. Lung CT in normal healthy people has different values in different respiratory states, -886+/-22HU at the end of deep inspiration and 699+/-52HU at the end of deep expiration. In summary, the normal values of lung CT are associated with different respiratory states, with different ranges of values at the end of deep inspiration and at the end of deep expiration.