Objective: To study the application value of ultrasound diaphragmatic function assessment in guiding mechanical evacuation of patients with mechanical ventilation, and to provide evidence for clinical application of ultrasonic weaning. Methods: Seventy patients who underwent mechanical ventilation and weaning in our hospital from October 2017 to May 2019 were selected for research. According to the success or failure of mechanical ventilation patients, they were divided into an experimental group (n=43) with successful weaning and a control group with negative (n=27). The function of the diaphragm in the process of weaning was evaluated by the distance between the right diaphragmatic displacement, the diaphragmatic contraction speed and the percentage increase of the diaphragm thickness measured by ultrasound in the two groups of patients during the spontaneous breathing test to analyze the value of application in the success of weaning. Results: The displacement distance of the right diaphragm was gradually increased with time during the spontaneous breathing experiment. At 0, 5 and 30 min, the displacement distance of the right diaphragm was significantly higher in the experimental group than in the control group (P<0.05); the contraction speed of diaphragm in the two groups of patients during the spontaneous breathing experiment gradually increased with time, and at 0, 5 and 30 min, the contraction velocity of the diaphragm in the experimental group was significantly faster than that in the control group (P<0.05). The percentage of diaphragmatic muscle thickness increase in the experimental group was significantly higher than that in the control group (P<0.05). When 1.15 cm was set as the critical value of the displacement distance of the right diaphragm, the sensitivity, accuracy and specificity of applying the suture success were 97.67%, 94.29%, and 88.89% respectively; when 1.45 cm/s was set as the contraction speed of the diaphragm, the sensitivity, accuracy and specificity of applying the successful weaning were 93.02%, 88.57%, and 81.48%, respectively; when 25% was set as the critical value of the percentage increase of the diaphragm thickness, the sensitivity, accuracy and specificity of applying the successful weaning were 97.67%, 95.71%, and 92.59%, respectively. Conclusion: The evaluation of ultrasound diaphragmatic function can effectively guide the clinical mechanical ventilation patients to withstand the machine. After the evaluation of the displacement distance of the right diaphragm, the contraction speed of the diaphragm and the increase of the thickness of the diaphragm muscle by ultrasound, the success rate of the patient's weaning is significantly improved, and the above indicators have high sensitivity, accuracy and specificity. Therefore, the evaluation of ultrasound diaphragmatic function has a high application value in guiding the mechanical evacuation of patients with mechanical ventilation, and can be widely applied in clinical practice.