The fault location of lighting arrester with hidden fault in existing 10 kV distribution network is easily affected by the size of grounding current. Aiming at the difficulty of the fault location of lighting arrester with hidden fault, focusing on the shielding ability of DC signal to cable capacitance current and the temperature risen characteristics of lightning arrester, a high-voltage DC constant current source applied to the hidden danger detection of gapless lightning arrester in distribution network is developed in this paper. Using the law of AC chopping voltage regulation circuit and the stable current characteristics of magnetic flux leakage transformer, Hall sensor is used to detect the signal and effectively shield the magnetic field. Combined with the test results of the relationship between the temperature rise of the arrester and the DC current, according to the direction relationship of the fault current on both sides of the fault point, the hidden danger of the arrester can be found effectively. PSCAD simulation and field actual fault data show that the DC signal generated based on high-voltage DC constant current source is injected into the line, the infrared temperature rises obviously, and is not disturbed by the hidden danger degree of arrester, which improves the robustness and accuracy of hidden danger finding of arrester. This work is supported by the National Natural Science Foundation of China (No. 51877135), the Science and Technology Project of State Grid Shanghai Electric Power Company "Research and Development of Safe Single Phase Grounding Fast Positioning System based on DC Constant Current Source" (No. SGSHQP00HBJS2001123).