Abstract: Rock arch is a type of remarkable landform in the danxia landscape area, and the large arch is usually named as natural bridge, which has important geomorphological meaning and tourism development value. The Yuehuyan arch is located in the western Xinjiang Basin of Jiangxi Province, which is a representative rock arch in the humid climate area of China. However, there were few reports on its formation process. The research in this paper conducted field survey, moisture test, observation under a polarizing microscope and salt chemistry experiment to study the characteristics and genesis of the Yuehuyan arch. The results show that both the NNE-trending and near EW-trending fractures controlled the spatial occurrence of the rock arch in the study area. The bedrock is composed of Upper Cretaceous aeolian sandstones of the Tangbian Formation, characterized by large-scale cross-beddings, high textural maturity and good permeability. They are conducive to dissolution weathering owing to low compositional maturity and abundant feldspar, lithic fragments and calcite cements. The sandstones at the intersection of fractures and bedding surfaces are prone to be broken, which is easily dissolvable under the action of river erosion, and the weathered materials were removed from the bottom of the rock mass. With the continuous dissolution weathering and collapse, the north and south flanks of the rock mass were eroded and penetrated into the arch eventually. This study provides solid materials for understanding the formation processes of arches in humid danxia landscape areas, which is significant for the protection and tourism development of arches.