For the early detection and for the treatment assessment of cardiovascular disease, improvement in range resolution of vascular ultrasound imaging is highly desirable. The employment of frequency domain interferometry with the Capon method largely improves the range resolution of ultrasound imaging; however, this methodology often underestimates the echo intensity. In this paper, we propose a compensation method to improve the estimation accuracy in echo intensity acquired by the high-range-resolution ultrasound imaging method based on frequency domain interferometry. The method requires 0.18 s/frame using a single CPU PC. The proposed method has the spatial resolution of 0.05 mm with the average estimation intensity error of 0.15 dB on the log scale, where we employ an ultrasound pulse of 7.5 MHz center frequency. We have applied the proposed method to a swine femoral artery in vitro and a human carotid artery in vivo, and verified its efficiency to improve the accuracy in echo intensity estimation.