We propose forward/lateral scattering of dual-wavelength (ultraviolet and short-wave near-infrared bands) radiation to simultaneously detect aerosol particles and fog droplet size distribution in an open atmosphere. The size distributions were described using a gamma distribution. A light-scattering detection system was optimized and designed, and the final wavelengths and scattering angles of ∼ 350 nm and ∼ 1100 nm, and 1°, 2°, 12°, and 35°, respectively, were selected. Numerical simulation analyses and measurements were performed for the proposed detection scheme. The results confirmed that the proposed method is feasible and can rapidly acquire the fog droplet spectrum and aerosol particle size spectrum distribution in an open environment. The system structure of the method is simple and easy to implement, with high detection results and accuracy.