Cardiovascular disease, a chronic and progressive arterial wall disease, is increasingly recognized for its clinical significance. Aminopeptidases N (APN), crucial in the pathophysiological processes of vulnerable plaque, have been linked to endothelial dysfunction, oxidative stress, and plaque formation, thus highlighting their potential as biomarkers for disease progression. However, current detection methods for APN in body fluids and in vivo have limitations, including insufficient sensitivity and specificity, time delays, and the inability to directly reflect enzyme activity in plaques. To address these challenges, we developed an optical probe, HD-APN, for in vivo imaging of aminopeptidases, providing a potential implementation in cardiovascular disease. Our work demonstrated the applicability of HD-APN for specific monitoring of aminopeptidase levels in plaques and serum, shedding light on its potential for further research in cardiovascular disease.