We present both simulated and experimental methods to show the propagation of linear and circular polarization under a settling smoke environment. Simulations and experiments were performed for artificial smoke with typical visible wavelengths under light and a moderate settling smoke environment. Using the Monte Carlo method, we simulate polarization propagation with the particle size, refractive index, wavelength, and the optical length under the settling smoke. Through the real-time measurement of optical length during the settling, the relationship of the settling environment parameters in the experiment and the simulation is established to improve the delay problem of the traditional parameters' measurement. Both the experimental and the simulated results show that with the increase of the concentration the degree of polarization of the four types of polarization is constantly decreased during the settling. Circular polarization persists better than linear polarization with the higher concentration, and the longer the wavelength, the better the persistence of the circular polarization. This study expands the application range of polarization under a settling smoke environment.