Intensive care unit acquired weakness (ICU-AW) is a common complication in patients admitted to the intensive care unit(ICU). Traditionally, ICU-AW is diagnosed by assessment of manual muscle strength, using the Medical Research Council (MRC) score, but it is difficult to perform in the ICU setting. Recent studies demonstrated that musculoskeletal ultrasound can detect the decrease in muscle volume and structural changes in critical patients at an early stage, which has a certain correlation with muscle function.This paper describs the current research progress of using musculoskeletal ultrasound to detect upper extremity muscles, diaphragm and lower extremity muscles to diagnose ICU-AW. We found that due to the small samples and few repeated experiments, the results of each experiment are often contradictory and a more accurate conclusion could not be obtained.Only changes in rectus femoris cross-sectional area (CSA) and echointensity have a moderate correlation with MRC score, which was statistically significant.In the future, more large-sample, repeatable experiments are needed to further investigate this question.