Objective To explore the effect of spectral CT single energy imaging for the diagnosis of coronary artery restenosis after stent implantation. Methods 80 review patients who underwent coronary artery stent implantation for 6 to 12 months were obtained as research objects, spectral CT single energy imaging (parameters of 55 kv) was executed. After 1 week, coronary angiography (CAG) examination was executed. On the basis of the CAG results, the diagnosis effect of spectral CT single energy imaging on coronary artery restenosis after stent implantation was evaluated. Results Using CAG results as a standard, the sensitivity of spectral CT single energy imaging for the diagnosis of coronary artery restenosis after stent implantation was 91.18%, the specificity was 90.83%, the positive predictive value was 75.61%, the negative predictive value was 97.06%, the accuracy is 90.91%; The diagnosis effect was better when diagnosing patients with circumflexartery stent or ＞3mm stent, the sensitivity, specificity, positive predictive value, negative predictive value, accuracy was 87.5%, 94.74%, 87.5%, 94.74%, 96.15% and 90%, 97.14%, 90%, 97.14%, 97.73%. Conclusion The spectral CT single energy imaging has good diagnosis effect on coronary artery restenosis after stent implantation, and is worthy of clinical popularization and application.