Objective To explore the feasibility of ultrasound diagnosis of diaphragmatic paralysis in patients with ventilation after congenital heart disease surgery. Methods There were 542 patients with congenital heart disease after surgery, difficult to be weaned off the ventilator or suspected diaphragmatic paralysis of the patients, respectively, in the ventilator continous positive pressure breathing (CPAP) mode and completely independent breathing state, whose ultrasound examination of diaphragm function was conducted to determine the presence of diaphragmatic paralysis in our hospital between January 1, 2013 and April 30, 2016. There were 327 males and 215 females at age of 14±32 months. The results of ultrasound diagnosis between ventilator CPAP mode and completely spontaneous breathing mode were compared. Results Five hundred and forty-two patients underwent ultrasound diaphragmatic examination. The results of bedside ultrasound were completely diagnosed: in completely spontaneous breathing, 82 patients who were diagnosed as diaphragmatic paralysis, including 39 on the right, 25 on the left, 18 on both sides; in CPAP mode, 82 patients who were diagnosed as diaphragmatic paralysis, 38 on the right, left 25, bilateral 19. Using ultrasound in CPAP mode to diagnose diaphragmatic paralysis after congenital heart disease surgery, compared with the completely spontaneous breathing state, the sensitivity was 100.0% and the specificity was 99.9%. Conclusion It is accurate and feasible to diagnose the presence of diaphragmatic paralysis in patients with ventilation after congenital heart disease surgery.