Objective:To analyze the consistency and repeatability of ultrasonography in diaphragm function evaluation. Method:Sixty healthy subjects participated in the present study,using a PA12A portable color doppler untra-sound diagnostic system.The diaphragm data were recorded during calm breathing and deep breathing,includ-ing diaphragm muscle mobility during calm breathing and deep breathing,diaphragmatic thickness during calm exhalation and calm inspiration,and diaphragmatic thickness during deep exhalation and deep inspiration.The in-tra-test reliability,inter-tester reliability and retest reliability of the above indexes were analyzed respectively. Result:For intra-test reliability,the intra-class correlation coefficient(ICC)values for diaphragm muscle mo-bility during calm breathing,diaphragm muscle mobility during deep breathing,diaphragmatic thickness during calm exhalation,diaphragmatic thickness during calm inspiration,diaphragmatic thickness during maximal exha-lation and diaphragmatic thickness during maximal inspiration were 0.99,0.99,0.99,0.99,0.99,0.99 and 0.99,respectively.The ICC values for the six indicators were 0.84,0.80,0.82,0.82,0.83,and 0.77 for in-ter-tester reliability.For retest reliability,the ICC values for the six indicators were 0.98,0.86,0.98,0.97,0.94,and 0.86 for relative reliability.The standard error of measurement(SEM)for the absolute reliability of the six indicators were 0.09,0.39,0.01,0.02,0.02,0.03,SEM％were 5.23％,8.40％,5.38％,5.7％,8.17％,8.77％,and the minimal detectable change(MDC)were 0.25,1.08,0.03,0.04,0.04,0.09,and MDC％were 14.49％,23.28％,14.9％,15.8％,22.64％,24.31％,respectively.Bland-Altman graphical analy-sis showed no systematic errors. Conclusion:Ultrasound has good reliability in diaphragm function evaluation and can provide objective evi-dence in clinical application.