Abstract: Load-bearing masonry walls resist most of the lateral loads in some in-service historical architecture. And the earthquake responses of the structures of these architectures are strongly affected by the seismic performances of the load-bearing walls. Because the blocks and mortar are of low-strength and have experienced long time of environmental effects, the seismic behaviors of the load-bearing masonry walls should be investigated specially for these architectures. A series of experiments were designed and carried out, in which the tested blocks were obtained from an old building undergoing retrofit. The age and constructional material of the old building are same with that of an in-service historical protective architecture. Compressive test specimens and wall panel specimens were prepared using these blocks and lime mortar. The ingredients of the lime mortar are same with that used in ancient architectures. Material tests and pseudo-static tests were then performed. The damage models，hysteretic energy dissipation and degradation of stiffness of the wall specimens were discussed. Through parameter calibration, a computer model was established to perform seismic analysis of the masonry wall. And the characteristics of load-bearing masonry walls of in-service historical architectures were presented. The proposed methods and results can be referred in further researches on seismic behaviors of in-service historical architectures.