For the measurement of particles size with backscattering method, the suitable range of particles size measurement have been presented by independent algorithm in Visual-infrared incident spectrum. We defined the range according to the retrieved results based on the analysis and comparison to many kinds of R-R distribution function. The simulation computation results showed that the particles size measurement range is from 0.05 mu m to 18 mu m with incident spectrum from 0.4 mu m to 2 mu m and different refractive index. The results retrieved were satisfied even if 1?% noise was added into the backscattering intensity.