Abstract: The experiments about aerosol deposition under dry and wet conditions were carried out on aerosol transport test facility which simulates AP series passive containment cooling. The results show that aerosol in atmosphere attenuates rapidly under wet condition due to diffusiophoresis deposition, in addition, the bigger the mass flux of steam condensation is, the rapider the aerosol attenuation speed is. It is confirmed that the design of passive containment cooling can enhance aerosol decay in bulk atmosphere by improving diffusiophoresis deposition. By taking the advantage of this feature, the reduction of radioactivity in containment can be enhanced through improving diffusiophoresis deposition of aerosol by increasing steam condensation.