Based on cluster-cluster aggregation (CCA) model, Monte Carlo method is taken to simulate the multi-particle size aerosol aggregates particles which consist of spherical original particles with different radius. According to electrical structure of substance, the aerosol aggregates particles are dispersed into a series of dipoles. By using discrete dipole approximation method, the values of optical characteristic quantities are obtained, such as scattering, absorption and extinction efficiency factors of multi-particle size aerosol aggregates particles with different incident wavelengths. Numerical results are compared with the characteristic quantities of the single particle size aerosol aggregates particles and the spherical aerosol particle of equal volume. Results show that the value of optical characteristic quantities of aerosol particles depends on the wavelength of incident light and shape of aerosol particles. There is significantly difference of the optical properties between single-particle size aerosol aggregates particles and multi-particle ones. The multi-particle size aerosol aggregates particles model is much closer to real aerosol particles. The findings provide a certain reference for comprehensive understanding and researching on the optical properties of aerosol particles.