The purpose of this study was to analyze the correlation between ultrasonic diaphragm contractile function and weaning respiratory monitoring after lung transplantation. Methods A total of 114 patients after lung transplantation in the Heart and Lung diagnosis and treatment Center of our hospital were divided into two groups according to the results of the first weaning test (Spontaneous Breathing Test, SBT) after lung transplantation. 93 patients in the weaning group and 21 patients in the weaning failure group. The respiratory function parameters were monitored during SBT, the diaphragm contractile function was evaluated by ultrasound, and the correlation between respiratory monitoring and diaphragm contractile function during weaning was evaluated by Pearson correlation analysis. Results There was a significant decrease in diaphragm function after lung transplantation. There was a certain correlation between DE and oxygen partial pressure, tidal volume, RSBI and ventilator days (r = 0.478, 0.734,-0.593,-0.567, P respectively < 0.05). Conclusion DE is correlated with oxygen partial pressure, tidal volume, RSBI and ventilator days, and can be used to evaluate respiratory function after lung transplantation.