Weaning difficulty is common in critically ill patients. Prolonged mechanical ventilation and weaning failure adversely affect the clinical outcome. How to better promote and achieve the early extubation is a very important subject. As a multi-dimensional monitoring method of important structure, function and morphology, critical care ultrasound which is helpful to improve our understanding and grasp of the core links in the respiratory circuit can comprehensively evaluate the state and reserve capacity of some important organs, such as the heart, lungs and diaphragm. It has great value in assessment of weaning and guided treatment. This paper will review the application of severe ultrasound in weaning.