A fractal shape model was used to simulate the morphology of fire smoke particles, as the aggregated spherical particles have intrinsical fractal structures. The shape model, whose parameters, including the total number of primary spherical particles in an aggregate, the fractal dimension and the radius of the primary particles, were obtained from a sequence of SEM images, was considered to be compatible with the smoke particle shape. The shape model was then used to compute the light scattering of smoke particles, and the results showed that, compared with the spherical particle with the same volume and other optical parameters, the fractal-like aggregate has smaller forward scattering and larger backward scattering.