This engineering project is an invention of high voltage diode 100 kV 20 mA with 100 kΩ using in high-voltage operations laboratory of electrical engineering department, faculty of engineering, Pathumwan Institute of Technology. Firstly we connected three low voltage diodes with 1000 V reverse bias in a plastic tube by series. Then each of tube was compounded by 100 diodes current 3 A. The resistors were combined in 33.75 Ω 200 W. The resistance to each parallel diode 2 MΩ. It must to do voltage rating that 100 kV and Internal resistance 100 kΩ after that do the test adout Features of high voltage forward bias diode and permanence of reverse bias .