Abstract: The glow plasma nitrogenization is an important approach to the heat treatment of processed workpieces in mechanical industry and the nitriding furnace′s performance is directly responsible for the heat treatment quality of the workpieces. Described in the paper are the working principle, technical modification solution and modification result of the grow plasma nitriding furnace. Owing to the modification the said heat treatment furnace works better than before with stable power supply quality, reliable arc extinguishing operation, shortened arcing time, reduced nitriding duration and higher nitriding quality of the workpieces.