Based on Bayesian theory, the compressive strength of existing masonry structure was deduced.The compressive strength of masonry tested by the method of axial compression in situ was taken as a prior information. At the same time, the estimated value of strength of block and mortar detected by the rebound method was used to construct the likelihood function, according to the calculation formula of compressive strength of masonry in the "Code for Design of Masonry Structures" (GB 50003-2011).Combining the prior information and the likelihood function, the posterior distribution of compressive strength of existing building masonry was derived.The research results show that the reasonable inferred values of compressive strength of existing masonry structures containing various information can be obtained through the posterior distribution. Moreover, the established posterior distribution can be used as the prior information for subsequent compressive strength Bayesian reference, which can realize the dynamic long-term observation of compressive strength of existing masonry structure.Furthermore,it provides a basis for the regular maintenance and reinforcement of existing masonry structure, and provides a foundation for the sustainable development of existing masonry structure.