In this study, a new media atomizing nozzle was adopted by rainfall simulation equipment for centrifugal model tests. Three comparative tests were conducted to simulate the behaviors of the deposits slope under the conditions of the rainfall and grid support. The scale of the centrifuge model to prototype was selected as 1:80. The displacement field of deposits slope was measured by a high-speed flash photography system, which had characteristics of non-contact and fixed-spot and was combined with program of particle image velocimetry (PIV). It was found that deposits slope was very stable without rainfall, but with increasing rainfall time, the settlement at top of slope and the horizontal displacement at surface of slope were both enlarged. Particularly, obvious deformation was observed on the surface of slope. Under continuous intensive rainfall, the slope failure mode was different from the traditional circular slide, since the slope failed layer by layer until a ‘debris flow’ was generated. However, the stability of the slope was significantly enhanced once protective geogrids were applied. Thus the application of geogrid supports efficiently improve the slope stability under rainfall conditions.