Aim To evaluate the significance of nuclear factor of activated T cells c1 (NFATc1) in diagnosing unstable plaques of coronary arteries referred to intravascular ultrasound (IVUS). Methods 183 patients with coronary heart disease (CHD) were divided into two groups of SA (with stable angina, 85 cases) and UA (with unstable angina, 98 cases) according to IVUS, another 46 patients without CHD confirmed by coronary angiography were taken as the controls. The expression of NFATc1 was measured by flow cytometry, then judged by creating the receiver operating characteristic curves (ROC). Results The expression of NFATc1 was significantly increased in patients with CHD, and the expression of NFATc1 in UA group was higher than that in SA group. Area under the ROC of NFATc1 was 0.796, P＝0.01, the optimal operating point was 17.5. Conclusion Detection of NFATc1 would be useful for diagnosing unstable plaques of coronary arteries, and be better for evaluating the risk of CHD and predicting acute coronary events.