Objective: To observe the effect of direct percutaneous coronary intervention (pPCI) followed by stent implantation and dilation on the short - and long-term prognosis of patients with ST segment elevation myocardial infarction (STEMI). Methods: A retrospective study was conducted on 70 STEMI patients treated at Luoyang Xinlicheng Hospital from June 2022 to October 2024. These patients were divided into a control group and an expansion group based on whether they underwent post-dilatation after pPCI stent implantation. The control group (n=31) did not undergo dilatation after pPCI stent implantation, while the expansion group (n=39) underwent dilatation. The short- and long-term prognoses of the two groups were compared Results: Patients in the expansion group had significantly higher stent diameter, stent length, and maximum pressure during stent implantation compared to the control group (P<0.05). The hospitalization duration in the expansion group was shorter than that in the control group, with a significant difference (P<0.05). There was no significant difference in the incidence of adverse cardiovascular events within 3 months after surgery between the two groups (P>0.05). After a 6-month postoperative follow-up, no significant difference was observed in the overall incidence of adverse cardiovascular events between the two groups (P>0.05), with a significantly lower incidence of target vessel revascularization in the expansion group compared to the control group (P<0.05). Conclusion: For STEMI patients undergoing pPCI treatment, the safety of post stent dilation is similar to that of non post stent dilation. Implementing post stent dilation is beneficial for reducing hospitalization time and decreasing the incidence of target vessel revascularization.