Abstract: Most of the geological bodies are covered by different thickness of weathering layers and dense vegetation due to the warm and humid climate in South China. Therefore, most optical remote sensing images reflect the spectral information of the vegetation layer, and which resulted in the difficult for the geological interpretation and mapping. In this paper, the ALOS-PALSAR dual-polarized SAR images and the Landsat8 OLI multi-spectral images have been interpreted jointly in Luoding area, western Guangdong. The result showed that joint interpretation can effectively increases identifiable species of lithology, and could be popularized for the mapping in strongly weathered areas of south China.