The theoretical expressions describing the self-mixing interference laser frequency, output power, and linewidth under the weak feedback of atmospheric particles are deduced based on the Mie scattering theory, the three-mirror theory and the steady-state equations of laser. The theory model of self-mixing effect feedback from atmospheric particles is established. And the relationship between the self-mixing signals and the physical parameters of atmospheric particles is analyzed in detail. The result shows that in a certain particle size range, the laser self-mixing signal intensity increases with the particle size and then decreases. With the increase of the real part and decrease of the imaginary part in atmospheric particle complex refractive index, the location of the external feedback strength peak value gradually moves to larger particle size. The amplitude of self-mixing signals is exponential decay with the increase of the external feedback cavity; the fluctuation frequency of the laser intensity is linearly related to the velocity of atmospheric particles. These conclusions offer a theoretical guidance to study optical sensing applications of atmospheric particles physical parameters by using the laser self-mixing technology.