The Late Cretaceous Hekou Formation in the Longhushan Global Geopark constitutes the bedrock of the present-day Danxia landforms. A large number of different cavities found along the rock cliffs are an important element of Danxia scenery system. The origin of these cavities has stimulated great interests among geologists and geomorphologists for a long time. One outcrop section and the three-dimensional size,shape and lithology of 383 cavities were measured and recorded. The research results showed that the cavities were largely caused by differential weathering related with lithologic changes. The outsized pebbles and concentrated pebbles were easily weathered to form small cavities. The interbedded sandstone beds between the conglomerate beds were readily weathered to generate intermittent cavities,which were coalesced to form rock toughs and flat cavities because of continuous weathering. The rapid water flows caused by torrential rains had an important effect on the formation of the cavities. The vertical distribution pattern of the cavities were produced by erosion on the cliff faces. In addition,the water erosion,chemical and physical weathering,microscale climate changes,and biological activities also possibly enhanced the enlargement of the cavities. The rock walls would become unstable and suffer from sudden collapse at the late stage of the cavity development.