Pulmonary fluid refers to a thin and continuous liquid layer mainly consisting of airway mucus and lining liquid on the inner surface of alveoli, which is essential for maintaining a healthy lung. This paper introduced the clinical significance of rheological properties of pulmonary fluid in airway stability, pulmonary barrier and clearance functions, ventilator induced lung injury and surfactant replacement therapy in infant respiratory distress syndrome. Furthermore, a variety of classical methods for measuring surface tension and liquid viscosity, such as Langmuir-Wilhelmy balance, captive bubble method, glass capillary viscometer and rotational viscometer, and emerging techniques (e.g. particle tracking microrheometer and axisymmetric drop shape analysis) were reviewed. A comparison of their advantages and drawbacks makes an important reference for the assisted diagnosis and treatment of lung diseases in clinical practice.