In machining and manufacturing area, surface roughness of metal object can affect performance of machining parts, so detection of roughness is very important. There are a lot of methods of roughness measurement, but many of them are contact measurement, not convenient and quick. Maybe some methods cause damage on workpiece surface to a certain degree. Aiming at a noncontact roughness measurement method, the laser interference technology was used for the metal surface roughness measurement. A set of detection system was set up. A suitable filtering technology was chosen to measure toughness and to improve the detection accuracy.