Decayed and insect attacked ancient poplar and larch wood components from the buildings of Tibet were inspected by a stress wave meter（FAKOPP）.The decay in each wood component was observed and classified after having been measured by FAKOPP.The comparison between the stress wave evaluation and visual classification showed that internal wood decay and insect infestation on ancient wood components could be detected accurately by stress wave.The decay situation evaluated by stress wave was almost consistent with the visual classification.Based on the results,the authors determined that visual observation combined with stress wave methods could examine the degradation of wood members in ancient buildings.