This paper proposed a method for predicting failure loads of masonry wall panels subject to uniformly distributed lateral loading based on a concept of structural stress state. Firstly, the characteristics of the structural stress state of masonry wall panels subjected to uniform distributed lateral loading were investigated through experimental results. Then, a new parameter was proposed to characterize the structural stress state. Next, the relation of the failure loads between a specified base wall panels and other wall panel was established using the proposed parameter. In this way, a method (called a ST method) based on a structural stress state parameter to predict the failure load of masonry wall panel from the base wall panel was established. The following case studies validated the ST method by comparing the predicted failure load with the experimental results, as well as those predicted from the existing yield line theory (YLT), the FEA method and the GSED-based cellular automata (CA) method. The ST method provided an innovative way of structural analysis on the basis of structural stress state.