Abstract: The transportation characteristics of aerosol particles in capillaries were studied with Monte Carlo simulation based on the diffusion model of aerosol particles,and the relationship between penetration and flow velocity was also investigated.It was shown that the penetration of aerosol particles significantly depended on the mean flow velocity.The penetration of aerosol particles remarkably increased with increasing mean flow velocity.It was also found that the mean retention time,half-peak width and penetration derived from the simulation were virtually consistent with experimental results.