Abstract: Arch dam and its rock foundation are taken as an integral coupling object of study. The constitutives of dam concrete or foundation rock are nonlinear elasticity. Different failure criteria of concrete and rock are used according to different stress state. Different constitutive modules and different elastic matrices are used according to the modes of fracture. The softening section of stress-strain relationship is considered in analysis of crack on arch dam and in rock foundation. Lastly, the flow diagram and a nonlinear analysis example of arch dam are presented.