Recently,laser particle sizer has been widely used in powder technology. This kind of instrumentation is based on the Fraunhofer diffraction. The accuracy in small size range is,therefore, not sufficient. In this paper, the Fraunhofer diffraction and Mie scattering theory are used, i.e, in large size range, the Franhofer diffraction, while in small size range, the Mie scat-teing. The measuring accuracy in small size range is thus improved. This leads to the performance improvement of laser particle sizer in the whole size range.

Keywords：laser particle sizer;fraunhofer diffraction;Mei scattering.