In the Wenchuan seismic region, solid material transport by landslides on hillslopes to channels has increased, increasing the susceptibility of debris flow in this seismic region. Timely and accurate mapping of the solid material transport potential of landslides on hillslopes is important for sediment management and debris-flow risk management. To rapidly and accurately understand the spatial distribution of the solid material transport potential of landslides on hillslopes in seismic areas, a new normalized index of the solid material transport potential of landslides on hillslopes (NDIH) was proposed to quantify the potential of solid material transport by landslides on hillslopes in drainage systems on the basis of remote sensing data and GIS platforms. The new approach was applied to 56 debris-flow basins in the epicenter of the Wenchuan seismic region, and the assessment results indicated that the regions between Gengda and Caopo had a greater potential for solid material transport by landslides on hillslopes in drainage systems, thereby increasing the susceptibility of debris flows at the beginning of the Wenchuan earthquake. Simultaneously, field investigations and remote sensing surveys were used to verify the rationality and reliability of the new method, and the area under the curve (AUC) of the ROC curve was 0.81; i.e., the results of the verification revealed that the NDIH can provide an accurate map of the solid material transport capacity of landslides on hillslopes, which was almost consistent with the findings of the field investigations. Compared with existing methods, the NDIH method has greater flexibility and applicability for revealing the potential of solid material transport on hillslopes in drainage systems in different geographical and climate regions.