More and more old dams are operated for more than 50 years. Evaluation on the life span and the real safety status becomes a challenging task for the dam society, especially for China because of more than 6000 dams to be evaluated and rehabilitated within the next 3 years. Based on the investigation on FENGMAN gravity dam, which is 91.7m high, operated from 1943 and suffered too much up lift pressure, freeze and thaw problem, etc., discussions on the life span evaluation of the old concrete gravity dams have been made. The
reasonable coefficient of dam safety has been discussed and rehabilitation schemes have been recommended. Meaningful results have been achieved based on the case study.