Yungang Grottoes, a world cultural heritage site,have been subjected to severe degradation due to natural and human factors over the years. Since January 2010, a site investigation on damage at the Yungang Grottoes has been carried out by the laboratory of Cultural Relics Conservation Materials of Zhejiang University, together with the Cultural Relics Protection Center in Xi’an and the Cultural Research Institute of Yungang Grottoes. The classification of and statistics on the damage,based on the categories and levels of damage,are presented.This report is part of the research done under the state science and technology support program and describes the need for damage prevention and restoration work of stone relics. The paper describes five main categories of damage:surface pollution and discoloration, surface weathering, surface biodegradation, preservation remains and water spots. Furthermore, the damage causes could be classified into 12 categories:dust pollution, smoked crusts, yellow spots, graffiti, grease, etc. The total polluted area is 7059.66m². the causes of the damage and the degree of the damage were analyzed. This research provides scientific data to guide future cleaning and conservation of the Yungang Grottoes. Further research topics, such as how to evaluate the level of damage, whether pollutants should be removed and how best to preserve the site with “minimal effort”.