Ultra High Voltage (UHV) transmission lines, which is a international leading technology independently developed in China, is an important part of the future power grid construction. It plays an important roles in the country"s future power grid construction and smart grid strategy to promote intelligent UHV transmission line inspection equipment research and engineering applications. UHV porcelain insulator detector is designed based on ARM Cortex-M4 processor. The detector"s main function is to measure the impedance of the insulator. It also has the functions that smart start or shut down a high-voltage module, real-time data displaying, analysis and judgment of the low-zero value and information storage. Detector is designed based on operating requirements of UHV power line tower site staff. The measurement accuracy of our detector is less than 3%, better than the existing EHV insulators detectors which have the measurement accuracy of 5%-10%.