Abstract: A micro-scale measurement system based on single-slit diffraction is designed. The system changes tiny scale determination into the variable slit-width by mechanical lever，through the detection of single-slit diffraction fringes to obtain the micro scale of test objects. The measurement results of standard feeler show that the system has high accuracy，easy operation，reliable measurement result and so on.

Key words: single-slit diffraction, micro-scale measurement, lever