Objective:To analysis the dangerous factors of root caries in the old people. To select the best methods of root caries. Methods:Clinical analysis the aged people were surveyed for abrasion and root caries. Results:Gingival recession ,dental plaque index ,age ,and sugar taking habit contributed significantly to the coefficient of determination. Conclusion:Gingival recession ,dental plaque index ,age ,and sugar taking habit can server as a guidance for the root surface caries prevention of the aged. Effective cracked tooth of therapy ,endodontic treatment can be prevention methods.