The numerical study of nanoparticle deposition in a fully developed laminar flow under different conditions is presented. The diameter of the particles ranged from 20 nm to 200 nm and the density was 1060 kg/m3. The calculated results show that the small particles deposit on the wall surface more easily. More large particles deposit on the bottom wall than on the upper wall. Under the laminar conditions, the number of particles that deposit is independent of the flow velocity. The smaller the flow region is, the more the particles deposit on the wall. The longer the particles remain in the flow, the more the particles deposit on the wall, and greater the difference between the number of particles depositing on the bottom wall and the upper wall.