To explore the predictive value of strong ion gap on the severity of septic AKI injury, and to provide reference for the diagnosis, treatment and recovery of septic AKI. Methods 322 patients with sepsis admitted to ICU of our hospital from October 2018 to October 2020 were selected and divided into experimental group and control group according to whether AKI occurred. The experimental group was divided into three stages according to the stage. The level of SIG, the correlation between PSIG and APACHE Ⅱ score, length of hospital stay, and SCR in the three groups were evaluated. The predictive value of SIG, APACHE Ⅱ score, and SCR in the severity of toxic AKI was evaluated by the receiver operating characteristic curve. Results Sig was positively correlated with APACHE Ⅱscore, length of stay and SCR. Pearson correlation analysis showed that the correlation was 0.4780, 0.2924 and 0.9700 respectively. The sensitivity, specificity and accuracy of SIG were 75.00%, 93.03% and 90.82% respectively. The corresponding values of SCR were 81.82%, 90.91% and 89.80% respectively. The corresponding values of APACHE Ⅱ were 55.56%, 97.75% and 93.88% respectively. The AUC of SIG, SCR and APACHE Ⅱ were 90.2%, 82.6% and 65.8% respectively. Conclusion Sig is positively correlated with APACHE Ⅱ score and SCR, and SIG has higher sensitivity, specificity and accuracy in predicting the severity of AKI injury in sepsis.