Objective: To explore the effect of blood glucose variability on no-reflow after percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI). Method: The clinical data of 149 patients with STEMI admitted to our hospital from March 2022 to March 2024 were retrospectively collected. All patients completed elective PCI. Immediately after the operation, the coronary blood flow was evaluated according to the thrombolysis in myocardial infarction (TIMI) blood flow classification, and the patients were divided into the non-reflow group and the normal blood flow group. Evaluate and compare the evaluations of blood glucose variability [Mean Amplitude of Blood Glucose Fluctuation (MAGE), glycemic Instability Index (GLI), coefficient of variation of blood glucose (GluCV)] between the two groups. Collect and compare the baseline data and blood glucose variability parameters of the two groups. Logistic regression was used to analyze the influencing factors of no-reflow in STEMI patients after PCI. The restrictive cubic spline model was used to analyze the dose-response relationship between blood glucose variability parameters and no-reflow in STEMI patients after PCI. Draw the decision curve of blood glucose variability parameters for evaluating no-reflow in STEMI patients after PCI. Result: Among the 149 STEMI patients, 31 cases had TIMI blood flow of grade 0-2, accounting for 20.81% (31/149), and were included in the non-reflow flow group. 118 cases had TIMI blood flow of grade 3, accounting for 79.19% (118/149), and were included in the normal blood flow group. The stent length in the non-reflow flow group was significantly longer than that in the normal blood flow group, and MAGE, GLI, and GluCV were significantly higher than those in the normal blood flow group (P < 0.05). There were no significant differences in other baseline data between the two groups (P > 0.05). Logistic regression analysis showed that the time from onset to admission, stent length, MAGE, GLI, and GluCV were the influencing factors for no reflow after PCI in STEMI patients (OR > 1, P < 0.05). Through the analysis of the restricted cubic spline model, the association intensities of MAGE, GLI, GluCV and no reflow after PCI in STEMI patients showed a linear dose-response relationship. The decision curve plotted showed that within the threshold range of 0.01-0.93, the net benefit rate of the combined evaluation of MAGE, GLI, and GluCV for no reflow after PCI in STEMI patients was significantly better than that of a single indicator, with the maximum net benefit rate being 0.208. Moreover, within the high-risk threshold range of 0.01 to 0.93, the net benefit rate of the combined assessment of the three is > 0, which is of clinical significance. Conclusion: Glycemic variability is closely related to no-reflow in STEMI patients after PCI, and MAGE, GLI, and GluCV are the influencing factors of no-reflow in STEMI patients after PCI.