Objective To investigate the influence of straightening phenomenon caused by stent implantation on biomechanical environment changes in vascular lesions, so as to explore biomechanical mechanism of restenosis and stent optimization. Methods Based on the computed tomography (CT) images of a patient, the balloon model, the left anterior descending coronary(LAD) artery model and two stent models (idealized stent and straightened stent) were reconstructed by Mimics, Geomagic and Pro/E software. The balloon-stent-LAD artery mechanical models were then established with the ABAQUS software. Based on the numerical simulation results, the influence of straightening phenomenon on mechanical environment at vascular lesions was analyzed. Results When the stents were expanded under the same inflation pressures (1.013 MPa), the Von Mises stress increased on vascular wall of the straightened stent model compared with the idealized stent model, and stress concentration occurred especially at the proximal and distal area of the stented regions and on the myocardial surface. The average and the maximum Von Mises stress on vascular wall of the idealized stent model were 0.39 MPa and 5.12 MPa, respectively. The average and the maximum Von Mises stress on vascular wall of the straightened stent model were 0.45 MPa and 7.43 MPa, respectively. Conclusions The straightening phenomenon caused by stent implantation would change the distribution of Von Mises stress and induce stress concentration. This kind of mechanical environment would cause greater damage to vascular wall, then might cause mechanical injury and vascular remodeling, leading to a higher risk of neointimal hyperplasia and subsequent restenosis. The research findings will be helpful for explaining the mechanism of in-stent restenosis, and may provide clinical guidance for the interventional surgery and optimization of stent design.