Abstract: In order to measuring the small variation of the steel-wire＇ s length, a leveling bench of high precision is made with laser, reflector, etc. The small variation of the steel-wire＇s length can be obtained by measuring the displacement of leveling bench with micrometer. The improved device is scientific and highly accurate, to be understood easily and mastered by student.

Key words: Young＇ s modulus, leveling bench, reflector, He-Ne laser, spiral micrometer