Test data of reinforced masonry shear walls failed in shear with thickness of 290 mm under cyclic load were employed to establish a criterion for judging the failure loads of reinforced masonry shear walls based on stress state. The relationship between the structural stress state and external load was deduced, and the concept of bearing capacity envelop was introduced based on the failure mechanics of the wall at different stages. By combining the stress state-load relationship with the bearing capacity envelop, a stress state-based criterion was established to judge the crack, failure and ultimate loads of shear walls, which was validated through the comparison between the calculated results and the test results. The proposed criterion provides a new way for structural analysis and extents the application of test data.