Content and research progress in nondestructive testing of wooden structures in ancient architecture

China has a large number of ancient wood structure buildings. To test and evaluate the condition of ancient wood structures reasonably and effectively is demanded by condition assessment of the wooden structures for protection and restoration of the buildings. Nondestructive testing of ancient wood structures is a test and evaluation technique to wood properties, oriented by inspecting and evaluation of wooden structure safety, and in situ application and actual inspection demands. The testing content mainly includes two aspects: nondestructive testing of defects and nondestructive testing of physical and mechanical properties. Assessing concealed defects of wooden structures and wood members is the main task and difficult work of the nondestructive testing of ancient wooden structures. Firstly, this paper introduces the composition of wooden structures of ancient buildings, and summarizes the nondestructive testing content and current common nondestructive testing methods. Then, the application and research progress of the inspection of concealed defects, the classification of wood members and the influence of decay on mechanical properties of ancient wood were summarized. Finally, the research status of nondestructive testing of ancient wood mechanical properties and effect of natural aging on wood properties of ancient buildings were summed up. The paper should be able to inspire and help relevant people who engaged in the inspection application and scientific research of protection technology of ancient building wood structures.