Aiming at the Stokes scattering matrix of smoke particles, an experimental setup was designed and built with an electro-optic modulation, a quarter waveplate, polarizers and a lock-in amplifier. Through the setup, the angular distributions of the Stokes scattering matrix were measured for the smoke particles generated from smoldering cottons, flaming heptane and smoldering sandals. The results show that the non-sphericity of smoke particles, especially the gray smoke particles, plays an important role on the light scattering. There are some shortcomings for Lorenz-Mie theory, which is based on a spherical model, to analyze the light scattering by smoke particles. In this case, it is suggested that non-spherical models are required to analyze the characteristics, e.g. intensity and polarization ere, of light scattering by smoke particles.