Atomic structure of gold nanowire with sub-nanometer diameter is investigated by interactive molecular dynamics (IMD). IMD is developed as original code using OpenGL graphics and computation of conventional molecular dynamics (MD) based on FS-type interatomic potential. Tensile testing of 7-3 type nanowire is performed, where comparison between results obtained by ordinary MD and by IMD is done. Necking before breakage is observed in both cases, but unique long one-dimensional atomic chain is realized by IMD more easily. This is owing to ability of delicate steering furnished by interactive simulation, which is realized conceptionally by exchange of physical information between simulator and computing system and technically by real-time visualization and easy-to-use device.