Abstract: Scattering phase functions and lidar ratios of natural aerosol aggregates at different ratios of dust and sea-salt were carried out based on discrete dipole approximation (DDA) for the size parameters from 0.1 to 25. Curves of scattering phase function and lidar ratio for natural aerosol aggregates as a function of scattering angle were almost the same. Scattering phase functions had distinct opposition effect for the size parameters from 13 to 24, which was most evident around the size parameter of 18. The effect of increasing dust on scattering phase function of natural aerosol aggregates were greater than that of increasing sea-salt, and the main influence range of the size parameter was from 15 to 25. These effects were distinct at different scattering angle except for the backscattering with the scattering angles around 180. The lidar ratios of natural aerosol aggregates had the maximum value of about 180 around the size parameter of 3. Influences of composition variations on lidar ratios were not large for the size parameters from 0.2 to 25, especially for the size parameters from 0.5 to 2 with the differences less than 1%.