Aim To explore the relationship between coronary artery disease（CAD） and the level of plasma Klotho protein in the aged. Methods A total of 138 patients over 60 years old with CAD （ experiment group） were enrolled， including 65 cases of single vessel lesion，73 cases of multivessels lesion. And a total of 140 controls above 60 years old without CAD were chosen. The levels of plasma Klotho protein were detected and compared between the two groups. The degree of coronary artery stenosis were assessed by Gensini scores. The correlation between coronary artery stenosis degree and the level of plasma Klotho protein was analyzed simultaneously. Results The level of plasma Klotho protein in experiment group was lower than that in control group. Moreover, the level of plasma Klotho protein in multivessels lesion group was lower than that in single vessel lesion group. The coronary artery stenosis degree was negatively correlated with the level of plasma Klotho protien. Conclusion The level of plasma Klotho protein may reflect the degree of coronary stenosis and could be used as an index to estimate the coronary artery stenosis degree.