Objective To investigate the prognostic value of the ratio of liver volume（LV）to estimated liver volume（ELV）（LV/ELV%）combined with platelet（PLT）in patients with chronic acute liver failure（ACLF）. Methods Retrospective analysis was made on the clinical data of 76 patients with ACLF who were diagnosed and treated by Nantong Third People′s Hospital from January 2020 to August 2022 and underwent abdominal CT exami⁃ nation within 3 days after admission，The patients were divided into survival group and death group according to the prognosis of 90 days after admission，and the correlation between LV/ELV% and PTA，ACLF prognostic models was analyzed. Multivariate logistic regression was used to analyze the risk factors affecting the prognosis of patients with ACLF，and a prediction model of LV/ELV% combined with PLT was established；ROC curve was used to analyze the clinical efficacy of LV/ELV% and platelet alone and in combination；The optimal critical value of LV/ ELV% combined with PLT for predicting the prognosis of ACLF was calculated，and the survival curve was drawn by Kaplan Meier method.Results The scores of TBIL，INR，PTA，PLT，LV，LV/ELV%，CTP，MELD and iMELD were significantly different between the two groups（P < 0.05）. Pearson correlation analysis showed that LV/ELV% was positively correlated with PTA（r = 0.4823，P < 0.001）and negatively correlated with CTP score（r = -0.3437， P = 0.0024），MELD score（r = -0.3109，P = 0.0063）and iMELD score（r = -0.3022，P = 0.0080）（P < 0.05）. Multivariate analysis showed LV/ELV%（OR = 0.965，95%CI：0.941 ~ 0.991，P = 0.007）and PLT（OR = 0.986， 95% CI：0.975 ~ 0.998，P = 0.020）were independent risk factors affecting the prognosis of patients with ACLF. The area under the ROC curve（AUC）of LV/ELV% combined PLT was the largest（AUC = 0.83，95% CI：0.73 ~ 0.92），which was higher than the scores of LV/ELV% alone（AUC = 0.79，95%CI：0.68 ~ 0.90）and PLT（AUC = 0.69，95%CI：0.57 ~ 0.81）. The optimal critical value of LV/ELV% combined with PLT was 0.63. Kaplan Meier survival analysis showed that the 90 day survival rate of patients with LV/ELV% combined with PLT < 0.63 was 78.18%（43/55），which was significantly higher than that of patients with LV/ELV% combined with PLT ≥ 0.63 （9.52%（2/21），and the difference was statistically significant（P < 0.0001）. Conclusion LV/ELV% combined with PLT can improve the predictive efficacy of LV/ELV% and PLT alone in predicting the prognosis of patients with ACLF：LV/ELV% combined with PLT ≥ 0.63 group indicates poor prognosis.