Abstract: Three-dimensional finite element analysis has been carried out for the interactions between the gravity arch-dam and the complicated foundation of Geheyan in Qingjiang River. Special attentions have been paid on the stress and displacement of the dam body, the regularity of stress and displacement of structural surface in the foundation and the influence on the dam body stress by the no-tension characteristic of fault F10. The results of the analysis are helpful for the optimal design and construction of the dam. Moreover, it is also the first successful case for us to employ the PCAT microcomputer with a DS1-780 coprocessor board to make nonlinear analysis of three-dimensional finite element for the large scale and complicated subject in rock and soil engineering.