Abstract: In an attempt to improve the flexural bearing capacity and deformation capacity of the stone in the existing stone structure and thereby to prevent the fragility of the stone from being damaged.This paper puts forward the strengthening technology of bonded steel for flexural strengthening of existing stone slabs and carries out bending capacity tests to study the effect of the thickness and width(sectional area) of the reinforced steel plate on the bending behaviors of the stone slabs.The results showed that the brittle failure pattern of stone slab could be significantly and effectively improved by steel bonding reinforcement and the destructive pattern is ductile fracture with obvious flexural deformation.The flexural bearing capacity of bonded steel strengthened slabs was significantly improved, and the ultimate load was 60%~233% higher than that of unreinforced slabs.With the increasing of the thickness and width of steel plates, the effect of promoting the bearing capacity of slabs was more significant.Steel bonded stone slabs can effectively suppress the development of invisible micro cracks in the tensile area, significantly improving the ultimate tensile strain capacity at the bottom of the slabs, and thus increase the cracking load of stone slabs.With the increasing of the thickness and width of the steel plate, and compared with the unreinforced stone slab, the ultimate tensile strain of the stone increased to 79.75%~178.48%, and the cracking load of the reinforced stone slab increased by 60%~140%.Finally, through theoretical calculation, the calculation formula of flexural capacity of stone strengthened with bonded steel was established, and the theoretical calculation results were in good agreement with the experimental results.