Humidity has a significant impact on production and daily life.In industry,it is necessary to ana-lyze the humidity of exhaust gases;in agriculture,it is necessary to control the environmental humidity to promote better plant growth;and in meteorology,the humidity values are used to predict weather.Therefore,it is of great significance to achieve real-time monitoring of humidity.Current humidity monitoring is mainly realized by humid-ity sensors mainly made of materials such as cellulose,polymers,and metal oxides,which are difficult to have the advantages of high sensitivity and good stability simultaneously.It is necessary to find a suitable material for a hu-midity sensor that can balance these excellent properties.On this basis,a nanodiamond based humidity sensor is prepared,which has high sensitivity(1.1 × 106%)and good stability.By applying the nanodiamond based humid-ity sensor in respiratory monitoring,the respiratory rate and respiratory flow rate can be analyzed in real-time.