Abstract: Considering crack patterns in dams and the used grouting method, this paper establishes a calculation model of crack mechanical grouting in concrete dams, which accounts for the on-way resistant, the gravity impact and some actual cracks found in a dam construction project. The stress intensity factors of crack tips of the three different models under grouting are obtained through weight function method and integration.With different fracture toughness of the mass concrete, the allowable mechanical grouting pressures of variable cracks and three crack models are studied. Finally the specific grouting methods for the three cracks are proposed.