Abstract: The Longdong rock caves, exemplified by the Beishiku Temple in Qingyang, were primarily excavated in weakly cemented sandstone strata. These rock masses are characterized by loose structures, low cementation strength, and weak bonding along bedding planes, which predispose flat-topped cave roofs to stratified spalling. This study selected ten representative spalling caves in the Beishiku Temple, where field investigations were conducted to acquire geometric parameters and spatial distribution characteristics of the spalling damage. The findings indicate that stratified spalling in flat-topped roofs exhibits a distinct multi-stage progression. Cracks initially form in regions of maximum tensile stress at the base of the roof and gradually propagate upward, resulting in stepwise collapses and eventually the formation of an ultimate equilibrium arch. By comprehensively considering factors such as overburden load, bonding strength of bedding planes, end constraints, and horizontal tectonic stress, this study derived the asymptotic evolution process from a fixed-end beam to an ultimate equilibrium arch model. Mechanical models corresponding to each evolutionary stage were developed using principles of structural mechanics and elasticity theory. The research elucidates the staged failure mechanism and critical thresholds of stratified spalling in sandstone cave roofs. It enables accurate predictions of roof instability trends and provides a theoretical basis for evaluating roof stability and implementing preventive conservation measures. These findings offer valuable insights for the long-term preservation and sustainable protection of similar rock caves.