Peak expiratory flow rate monitoring and recording of asthma diary are important links in the prevention and treatment of bronchial asthma. Some data show that the proportion of Chinese asthma patients who have PEF monitoring and recording of asthma diary is low, and most of the judgments of asthma patients are made using retrospective assessment of symptom severity and the percentage of PEF to the expected value at the time of consultation, which may result in underestimation of the disease. Accurate judgment of asthma severity is a prerequisite for standardized asthma prevention and treatment, and only with accurate staging and grading can patients be given adequate treatment, otherwise it will result in inadequate treatment. PEF is a convenient and good indicator of asthma condition. In asthma control guidelines and GINA documents, it is recommended to use peak expiratory flow rate meter to detect the change of PEF in the morning and evening every day. The patients were evaluated and graded to decide the treatment plan. It is known that asthma is a chronic inflammatory airway inflammation involving multiple cells and cellular components, and this chronic inflammation causes airway It is known that asthma is a chronic inflammatory airway inflammation involving multiple cells and cellular components, and that this chronic inflammation triggers airway narrowing causing clinical symptoms, which can appear as transient worsening of the disease, sometimes only as a change in PEF, and that assessment of patient deterioration would be lost if based only on PEF measured at follow-up. This shows that the main reason for underestimation of asthma disease by recall and PEF testing at follow-up is that because the patient is not in an exacerbation state at the time of follow-up or the severity of the exacerbation is mild, the percentage of PEF measured at the time of the patient’s visit as a percentage of the expected value does not reflect the true condition of the patient over the 4 weeks, resulting in an underestimation of the disease. The clinical value of PEF monitoring is also reflected in the fact that PEF monitoring can detect minor changes in the condition of asthma patients earlier than clinical symptoms, and the implementation of PEF monitoring and asthma diary is of great importance for accurate diagnosis of the condition, timely rehabilitation interventions and rational treatment.