In the present work, the stable atom-scale iron quantum wire was electrochemically prepared and characterized successfully by a homemade electrochemically controlled system. By adjusting the resistance of the external resistor, the atom-scale iron wire with preset conductance would be obtained. When scanned with low bias, the iron quantum wires showed the linear ohmic relationship for the current-voltage curve. With an external resistor control, the diameter, aspect ratio can be easily tailored, so it was a simple and controllable method. In addition, with a pure water environment of the preparation, the method had a less interference of other ions and was more suitable for sensor study of the quantum wire. The work was greatly significant for material science, molecular electronics, chemical and biological sensing.