The scattering characteristic of fire smoke is a major aspect in fire smoke detection foundamental research. Based on Mie scattering theory, the paper presented some research on comparison between different algorithms. An improved algorithm was adopted to calculate the scattering intensity and its distribution in all directions. To verify the theoretical calculation results, a set of experiment was designed to measure the light intensity in three directions of different fire smoke. From the experiments results, it could be found that the results of calculation and experiment had a good accord. It can be concluded that the relative ratio of scattering intensity is an important parameter for certain material, and different kinds of smoke by this ratio.