Objective To investigate the expression of neutrophil gelatinase-associated lipocalin (NGAL) signaling pathways in the early stage of porcine vein graft restenosis, and to explore the possible role and mechanism in the early vein graftrestenosis after coronary artery bypass surgery. Methods We selected 18 ordinary healthy pigs weighing 25-30 kg and collected samples of the vein graft of pigs at the preoperation and postoperative days 7, 14 and 30. Hematoxylin-eosin (HE) staining and Masson staining, immunohistochemical method were used to observe the neointimal hyperplasia, the migration of smooth muscle cells and and vascular remodeling of the vein bypass graft. The expression changes of NGAL, matrix metalloprotenase (MMP)9, MMP2 and tissue inhibitor of metalloproteinase (TIMP)1 in different periods of the vein bypass graft was tested. Results By HE and Masson staining, with the passing of modeling time, degradation of collagen matrix in the vein graft, gradually thickening of muscle fibers and the migration to the inner membrance and vascular remodeling caused the vascular stenosis. By immunohistochemistry, NGAL, MMP9 and MMP2 of normal vein in the model were seldom expressed and even did not express. At 14 days after the modeling, NGAL expression in the membrane layer of blood vessels began to appear, peaked at postoperative 30 days, and began to appear in the inner membrance. MMP9, MMP2 expression began to appear at postoperative 7 days, peaked at postoperative 14 days, and tended to decline at postoperative 30 days. TIMP1 expression was less in normal vascular walls and at the 14 days after the modeling, expression peaked in the vein graft. Conclusion NGAL, MMP9, MMP2 and TIMP1 may be involved in the formation of early vascular graft restenosis. NGAL as initiator, results in the expression of MMP9 and MMP2, and participates in the degradation of collagen matrix and the migration of smooth muscle cells in vein grafts. TIMP1 as a negative factor, may play an important role in maintaining their own balance.