Pulmonary function test is an indispensable auxiliary test for the measurement of children′s respiratory function.As one of the most important parameters in lung function test, peak expiratory flow has important guidance in respiratory diseases, neuromuscular diseases, surgery and so on.However, in addition to respiratory diseases, up to now, physicians have insufficient understanding of the application of peak expiratory flow in other diseases.Therefore, the application of peak expiratory flow in various clinical diseases was summarized, aiming at improving clinicians′ understanding of peak expiratory flow.