Abstract: This paper analyses the influence of factors such as camera resolution and magnification, lighting type, surface condition, and scanning speed on the inspection resolution of CCTV (closed-circuit television monitoring system) inspection of the inner surface surfacing layer of Hualong No. 1 pressurised water reactor core power unit voltage regulator. It proposes to improve the CCTV inspection resolution by improving the resolution of the camera and monitor, using diffuse coaxial light and providing sufficient lighting. It also suggests to adopt sufficiently slow scanning speed, improving surface conditions and other measures. At the same time, effective image processing measures can enhance the typical characteristics and resolution of defects, so as to improve the detection rate of defect detection.