Against the background of the natural deposition of erosols in containment under severe accident conditions, a relevant experimental facility was designed and constructed to study the decay constant of the natural deposition of erosols. TiO₂ was used as the erosol medium, and the decay constant of erosols was studied. The results show that when erosol concentration is < 15,000/cm³, the decay constant of erosols increases with the increase of the particle size. However, when it is ≥ 15,000/cm³, because the agglomeration of small particles into larger particles accelerates the deposition of particles with smaller size, the decay constant of erosols decreases first and then increases with the increase of the particle size. In addition, the effect of electrostatic on the decay constant of the natural deposition of erosols was studied. When the electrostatic effect is present, the decay constant of erosols increases significantly. Finally, the natural deposition characteristics of erosols were obtained.