Interstitial lung diseases are a group of diffuse parenchymal lung disorders associated with substantial morbidity and mortality. As an indicator of alveolar epithelial cell destruction and regeneration, KL-6 is used for rapid, simple, economical, repeatable and non-invasive detection, which is superior to classical methods such as high-resolution lung CT, alveolar lavage and lung biopsy. KL-6 level in patient serum can be regarded as an indicator for early prevention of pulmonary disease.