In order to reveal the seepage law of the humid zone during the formation and evolution of the non-cohesive sandy channels under laboratory conditions, a system of circulating flume is designed. The influence of different factors on the regularity of riverbed seepage flow and the tempo-spatial variation of the moisture content in the riverbed was analyzed by controlling four parameters, which are sand particle size, inflow volume, riverbed gradient and riparian vegetation coverage. The results show that the permeability of coarse sand is much larger than that of fine sand, and the slope of the basin is proportional to the seepage flow. The riverbed with smaller initial moisture content has a larger seepage flow. When the control factors such as riverbed sand, gradient and riparian vegetation are certain, there is a relatively saturated seepage flow in the channel evolution tests. When the flow is greater than the relative saturation seepage flow, the seepage flow will remain relatively stable. In addition, the moisture content of the riverbed surface changes slightly at the time scale, but shows a stepped change from one region to another at the spatial scale.