Aim To investigate the association of triglyceride-glucose (TyG) index with microvascular obstruction(MVO) after percutaneous coronary intervention(PCI) in patients with ST-segment elevated myocardial infarction(STEMI). Methods Individual patient-data were pooled from 310 patients with STEMI underwent emergency PCI in Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School from June 2018 to June 2021 for a prospective analysis. A week following the operation, cardiac magnetic resonance imaging was used to evaluate the MVO region and the patients were divided into two groups based on whether MVO occured after PCI:the MVO group (n＝183) and the non-MVO group (n＝127). The clinical data of the two groups were compared, and the linear relationship between TyG index and MVO was described using restricted cubic splines(RCS). Univariate and multivariate Logistic regression analysis were used to correct for confounding factors and identify independent risk factors for MVO occurrence. Results After adjustment for confounding factors, TyG index was an independent risk factor for MVO after emergency PCI in STEMI patients, and every 1-unit increased in TyG index, the risk of MVO increased by 1.24 times (OR＝2.4,5%CI:1.07～4.71, P＝0.033). The RCS curve analysis results showed that there was a linear relationship between the TyG index and the occurrence of MVO after emergency PCI (non-linear correlation test P＝0.47).When the TyG index was greater than 9.5, the risk of MVO after emergency PCI significantly increased. ConclusionAn increased TyG index is postively associated with the incidence of MVO in STEMI patients who have undergone PCI, and has clinical significantce for early prevention and risk stratification of MVO in STEMI patients.