Objective To investigate the effect of baseline atherogenic index of plasma （AIP） on the long-term prognosis of patients with acute myocardial infarction （AMI）. Methods A total of 712 AMI patients admitted to the hospital from January 2018 to December 2019 were continuously included as subjects and divided into a low-value group （AIP < 0.280， n = 237）， a median-value group （AIP 0.280 ~ 0.852， n = 238） and a high-value group （AIP > 0.852， n = 237） according to the baseline AIP tertiles. The primary endpoint was defined as the occurrence of major cardiovascular adverse events （MACEs）. Multivariate Cox regression was used to analyze the independent influencing factors of MACEs. The nonlinear relationship between AIP and the risk of MACEs was analyzed with restricted cubic spline plots. Kaplan-Meier curve was used to analyze survival differences between groups. Subgroup analysis assesses the consistency of AIP's predictive value to MACEs. Results With the increase of AIP tertile groups， the proportion of dyslipidemia and MACEs increased， white blood cell count， fasting blood glucose， triglyceride， total cholesterol， low density lipoprotein and AIP increased， and high-density lipoprotein decreased， with statistical significance （P < 0.05）. Multivariate Cox regression analysis showed that AIP was an independent risk factor for MACEs （HR = 2.024， 95%CI： 1.211 ~ 3.381， P = 0.007）. The results of restricted cubic spline analysis show that there is an L-shaped nonlinear effect relationship between AIP and the risk of MACEs （P-nonlinear = 0.008）. When AIP > 0.613， the risk of MACEs in AMI patients increases with the increase of AIP. Kaplan-Meier survival curve analysis results show： With the increase of AIP， the cumulative incidence of MACEs in AMI patients increased significantly （Log-rank test， P = 0.032）. Compared with the low-value group， the risk of MACEs in the high-value group increased by 131% （HR = 2.311， 95%CI： 1.261 ~ 4.234， P = 0.007）. The results of subgroup analysis showed that the P value of interaction within each subgroup was not significant， and the ability of AIP to predict MACEs was applicable to all subgroups. Conclusion Increased AIP at baseline is an independent predictor of poor long-term prognosis in patients with AMI.