AbstractIn this paper, According to theoretical analysis of detection method of voltage, a new method of non-contact detection method of voltage is designed under any severe environmental conditions, for example, in coal mines. Being different from traditional detection method of voltage, electric-field state is detected using Field Effect Transistor (FET) as sensor of electric-field based on the capacitance effect principle. And then charged state of conductor should be detected by electric-field state indirectly. Whether or not there is current on conductor, charged state of conductor could be detected by this method. Therefore, it has excellent characteristics, such as simple structure, low cost, high reliability and sensitivity.