Intensive care unit acquired weakness (ICU-AW) is common in clinical practice, especially muscle weakness and muscle dysfunction caused by delayed weaning from mechanical ventilation, which requires timely and effective imaging evaluation. Ultrasound, as a non-radiation, non-invasive, real-time and repeatable imaging technology, can serve as a preferred method for assessing muscle structure and function, and has important clinical value in the diagnosis and monitoring of ICU-AW. This review summarizes the clinical application and research progress of ultrasound examination in the non-invasive quantitative evaluation of ICU-AW.