Abstract: The experimental study on flexural behaviors of eight full-scale stone beams (including four beams unstrengthened and four beams strengthened by CFRP) was carried out. The failure modes, flexural capacity and deformability were analyzed. The experimental results show that the unstrengthened stone beams exhibit a typical brittle failure mode while the strengthened stone beams demonstrate a partially brittle failure mode when they are damaged. Furthermore, the flexural capacity and deformation capacity of the strengthened stone beams are improved to some extent. The theoretical analysis of the flexural capacity of the strengthened stone beams was conducted, and a simplified calculation formula of the ultimate flexural capacity was proposed. After reaching the ultimate load, the strengthened stone beams still had certain flexural capacity, namely flexural capacity margin, because of the action of CFRP; this characteristic could avoid the serious consequences of sudden collapse of stone beams.