Under the influence of natural forces and human activities, earthen heritage sites in arid and semi-arid regions like Great Wall, Jiaohe Ruinsy, Beiting Ruins were hanged in the air largely by sapping at the base of the wall even causing partial collapse. In this study, rammed heritage sites with serious basal sapping were consolidated by rammed roof-propping, which conformed with basic conservation principles of cultural heritage sites protection and followed the requirement to conserve original material and technology, and also had good reinforcement effect. However, large-sized rammed roof-propping body produced big crack in 1-3 mm width from the original wall under the effect of consolidation and dehydration. Control and reduction of shrinking cracks between roof-propping body and original wall were the key to realize reliability and effectiveness of large-sized ramming repair. Based on the theory of consolidation and dehydration, this study conducted consolidation test with different density and gradation samples indoor, and collected the data of dehydration shrinkage of samples with different shapes. This study made a comparative analysis of the regulation of consolidation deformation and dehydration deformation in the condition of different densities and different clay particle gradations, and analyzed threshold value of consolidation and dehydration deformation for roof-propping body, according to traditional rammed technology and laboratory empirical formula. The empirical formula to control large-sized vertical deformation was preliminarily proposed, which can provide theoretical references for controlling shrinkage settlement of large-sized rammed roof-propping body.