Objective To analyze the risk factors of concurrent intensive care unit acquired weakness （ICUAW）in elderly patients with sepsis undergoing mechanical ventilation（MV），and to explore the early predic⁃ tive value of modified Nutrition Risk in the Critically ill（mNUTRIC）score for ICUAW. Methods 320 elderly patients with sepsis undergoing MV admitted to the ICU of our Hospital were enrolled and assigned to the ICUAW group（n = 98）and the non⁃ICUAW group（n = 222）according to whether ICUAW occurred. The general datas， mNUTRIC score and laboratory index at ICU admission were collected and compared.The incidence of ICUAW in different mNUTRIC score evaluation groups was compared. Multivariate logistic regression analysis and receiver operating characteristic（ROC）curve were used to explore the relationship between mNUTRIC score and concurrent ICUAW in elderly patients with sepsis undergoing MV. Results The age，body mass index，charlson comorbidity Index score，sequential organ failure assessment score，acute physiology and chronic health evaluation system Ⅱ score，mNUTRIC score，the proportion of septic shock，the duration of MV and serum lactate level in ICUAW group were significantly higher or longer than those in the non ⁃ ICUAW group，while the serum albumin level in ICUAW group was significantly lower than that in the non⁃ICUAW group（P < 0.05）. The percent of patients with ICUAW in different mNUTRIC scores with 0 ~ 4 points and 5 ~ 9 points were 6.28%，66.67%，respectively，and the difference was statistically significant（χ2 = 132.141，P < 0.001）. Multivariate logistic regression analysis showedthat concurrent septic shock（OR = 2.238，95%CI：1.099 ~ 4.555，P = 0.026），long duration of MV（OR = 1.131， 95%CI：1.019 ~ 1.254，P = 0.020）and elevated value of mNUTRIC score（OR = 2.508，95%CI：1.968 ~ 3.196， P < 0.001）were independent risk factors for concurrent ICUAW in elderly patients with sepsis undergoing MV. The ROC curve analysis showed that the area under the ROC curve，sensitivity and specificity of mNUTRIC score in predicting concurrent ICUAW in elderly patients with sepsis undergoing MV were 0.870（95%CI：0.828 ~ 0.905）， 87.76% and 80.63%，respectively. Conclusion mNUTRIC score at ICU admission has a high clinical value in predicting concurrent ICUAW in elderly patients with sepsis undergoing MV.