Abstract: With the continuous growth of power cable installations, cable bending has become inevitable due to the limited space conditions of civil engineering environments. Owing to structural constraints, power cables have strict requirements on bending radius during both laying and operation. If the bending radius does not meet the standard, the main insulation of the cable may be damaged, leading to potential safety accidents in power transmission. This paper reviews the traditional principles of bending radius measurement, existing measurement methods, and currently available devices, and analyzes their advantages and limitations. On this basis, a bending radius measuring instrument was developed, which is designed according to the theory of the circumcircle radius of a triangle and integrates hardware components such as angle sensors and laser displacement sensors. The proposed device can be applied not only to measuring the bending radius of primary and distribution power cables but also to scenarios such as highway interchanges and large-scale pipelines, thereby significantly improving the efficiency, safety, and convenience of bending radius measurement.