Requirements of surface quality of silicon wafer are increasingly restrict. Many investigations have been done to inspect defects on silicon wafer. However, rare studies have been reported on defect components inspection which is also critical to trace to the source of defects and monitor the manufacture processes in time. In order to inspect the components of contaminated particles on silicon wafer, especially with a high speed and in line mode, dual nanosecond pulse laser system both wavelengths at 532nm is designed in which one laser pumps the particles away from wafer surface almost without damage, the other laser breakdowns the particles in air above the wafer surface to obtain the emission lines of the contaminated particles by a spectroscopy with CCD. The sensitivity of the dual pulse laser system is evaluated.