Abstract：The method for inversing density changes of underground abnormal body with genetic algorithm by use of the repeated gravity data is described. The validity and stability of this method are proved by simulating trial calculation.The density changes before and after the first water impounding of Three Gorges Reservoir are inversed. Considering some possible situations of underground rock body’s density changes caused by the water impounding, four priori density contrasts are used to fit the remaining gravity changes obtained by repeat gravity data from April to July 2003 after deducting the gravity changes caused by the water loading. Some meaningful results are given.
