Objective To investigate the correlation between atherogenic index of plasma (AIP) and the severity of hypertriglyceridemic acute pancreatitis (HTG-AP) and the value of AIP combined with Bedside Index for Severity in Acute Pancreatitis (BISAP) score in the early prediction of severe HTG-AP (sHTG-AP). Methods A retrospective analysis was performed for the clinical data of 170 patients with HTG-AP who were hospitalized in The General Hospital of Central Theater Command from January 2017 to December 2021, and according to related guidelines, they were divided into the sHTG-AP group with 28 patients and non-sHTG-AP group with 142 patients. Peripheral blood samples were collected from all patients within 24 hours after admission, and the two groups were compared in terms of sex, age, laboratory test results, AIP, BISAP score, and modified CT severity index (MCTSI) score. The chi-square test or the Fisher's exact test was used for comparison of categorical data between groups; the Mann-Whitney U test was used for comparison of continuous data between groups. The Spearman rank correlation test was used to investigate the correlation between each factor and the severity of HTG-AP, and the binary logistic regression analysis were used to investigate the independent risk factors for sHTG-AP. The receiver operating characteristic (ROC) curve was plotted to assess the predictive efficacy of each indicator. Results There were significant differences between the two groups in the medical history of diabetes, lymphocyte count, albumin, Ca 2+ , triglyceride, high-density lipoprotein cholesterol, AIP, BISAP score, MCTSI score, length of hospital stay, and hospital costs (all P < 0.05). The sHTG-AP group had a longer length of hospital stay, higher hospital costs, and a higher AIP value. AIP (odds ratio [ OR ]=1.244, 95% confidence interval [ CI ]: 1.062-1.458, P =0.007), BISAP score ( OR =5.525, 95% CI : 1.646-18.543, P =0.006), and MCTSI score ( OR =2.029, 95% CI : 1.245-3.305, P =0.004) were risk factors for sHTG-AP. AIP, BISAP score, and MCTSI score were positively correlated with the severity of HTG-AP ( r =0.291, 0.631, and 0.649, all P < 0.001), and AIP was positively correlated with BISAP score and MCTSI score ( r =0.190 and 0.215, both P < 0.05). AIP had an optimal cut-off value of 1.095 in predicting sHTG-AP, and AIP, BISAP score, and AIP combined with BISAP score had an area under the ROC curve of 0.759, 0.887, 0.925, respectively, a sensitivity of 0.821, 0.857, and 0.786, respectively, and a specificity of 0.627, 0.817, and 0.937, respectively (all P < 0.001). Conclusion AIP is a risk factor for sHTG-AP and is correlated with disease severity, and AIP combined with BISAP score has a relatively high value in the early prediction of sHTG-AP.