Geological disasters such as landslides occur frequently in southern Jiangxi, mostly induced by rainfall and artificial slope cutting. Physical model tests, especially field model tests, are considered effective to reveal the mechanism of landslides. The case on a cutting slope featured with weathered metamorphic rock in southern Jiangxi is investigated, in which a self-designed rainfall simulation system is applied. The alignment of field instrumentation includes four boreholes for measuring water content as well as pore pressure and two monitoring points for displacement. An artificial rainfall was carried out on the site. The ground response in terms of water content of slope soil, pore water pressure, displacement from the rainfall process is investigated, and the infiltration manner of weathered metamorphic rock slope under continuous heavy rainfall is discovered. The deformation and failure mode of slope based on weathered metamorphic rock is concluded. The results show that there is a lag in the change of soil moisture content after rainfall. The moisture content performs continuously increasing with the infiltration of rainfall water, and the value decreases with depth. The log of pore pressure collected from the bore hole shows an obvious response to the rainfall condition in shallower layers, and the soil below the depth of 1 m stays unsaturated. The displacement at the monitoring point is obviously positively correlated with the rate of change of water content, and the slope deformation is mainly performed on the side of the slope where the water content changes significantly. The slope displacement shows obvious dependence on the change of the pore pressure. The dilatancy deformation of the soil inside the slope reduces the pore pressure value, resulting in the decrease of the rate of slope deformation. The deformation and failure process of a steep artificial cut-slope under heavy rainfall conditions can be divided into three stages: the scattering and slipping of the slope surface; the formation of tensile cracks on the platform; the overall collapse of the slope.