The main hall of Ningbo Baoguo Temple is the oldest and most integrated. Buddhism timber building in the south of the Yangtze River. But it has a serious damage now. In order to better preserve and repair the building, the research on structural performance and damage characteristic is necessary. This research is the scientific foundation of the repair. First, the damages of building were analyzed by the investigation on site. The visible problems were found out. Then the structural performance was researched by accurate survey and FEM analysis to research the potential problems. Finally, the repair suggestions of building were presented based on the results of damage investigation and theoretical analysis.