Objective · To investigate the expression of the regulator of calcineurin 1 (RCAN1) and calcineurin A (CnA) in tissues of in-stent restenosis after intervention of arteriosclerosis obliterans (ASO), and to explore the relationship between their expression levels and the occurance of in-stent restenosis. Methods · Superficial femoral arterial tissues were collected from 15 ASO patients undergoing lower extremity amputation for in-stent restenosis in Department of Vascular Surgery, The First Affiliated Hospital of Chongqing Medical University from September 2013 to June 2016. H-E staining and Masson staining were performed on the stenosis tissues, as well as on the proximal and distal tissues, and the morphological changes of these tissues were observed under optical microscope. Western blotting was used to detect the protein levels of RCAN1, CnA and proliferating cell nuclear antigen (PCNA). The distribution of RCAN1 and CnA proteins was observed by immunohistochemistry and immunofluorescence methods. In addition, co-immunoprecipitation was used to validate the protein-protein interaction between RCAN1 and CnA in vascular tissues. Results · The expression of RCAN1 in the distal tissues was significantly elevated compared with the proximal tissues and the stenosis tissues (P<0.05). The expression of RCAN1 in the proximal tissues was higher than that in the stenosis tissues (P <0.05). The expression of CnA and PCNA in the stenosis tissues was significantly elevated compared with the proximal tissues and the distal tissues (P<0.05). Immunohistochemistry and immunofluorescence analyses showed that RCAN1 and CN proteins were mainly expressed in the cytoplasm of vascular smooth muscle cells. Co-immunoprecipitation analysis showed there is protein-protein interaction between RCAN1 and CnA in arterial tissues. Conclusion · The low expression of RCAN1 and the high expression of CnA are probably related to the occurrence of in-stent restenosis.