Fractional exhaled nitric oxide (FeNO) is a simple, sensitive and non-invasive marker that can monitor eosinophilic airway inflammation. Its levels are influenced by height, weight, gender, ethnicity and smoking status. FeNO was first introduced as a biomarker to assist in asthma detection, and now plays an important auxiliary role in its diagnosis, management, and prognosis evaluation, including treatment guidance and drug efficacy assessment. With continuous exploration, exhaled nitric oxide has demonstrated utility in a variety of respiratory diseases, including chronic obstructive pulmonary disease, chronic cough and interstitial lung disease. It can also serve as a biomarker after lung surgery to indicate the risk of postoperative complications and impaired lung function. This article summarizes the clinical value of exhaled nitric oxide in common pulmonary diseases, aiming to provide a reference for its clinical application.