Abstract: Based on Mie theory, the scattering figure and extinction curve of spherical particles with different sizes are presented. The scattering figure of a spherical particle shows that the scattering angle becomes narrow as the size of a partical increases gradually. From these extinction curves, we can see as the size of particles increases, the extinction efficiency factor tends to 2. Finally, the variation of polarization degree of scattering laser with particle size and scattering angle. Theses figures about polarization degrees versus the size of particles show taht as the size of the partcle increases, the peak of polarization degree extends forward, but the polarization degree decreases.