Abstract:The concept of chemical damage is given and expounded. The mechanical effects of chemical damage from water and rock interaction are related to many complex processes. The mechanism of the mechanical effects of water-rock interaction on rock is explored by using the theory of chemistry,rock failure mechanics with chemical damage,the modeling method and the energy point of view. Using the theory of large mode and small mode on chemical action of water-rock,the reason why the strenuous deformation and failure of rock mass frequently occurred after torrential rain or human engineering activity in natural world is expounded. The ways of quantitative methods for the chemical damage of water-rock interaction are approached. The division into districts of the chemical damage levels in rock is proposed. The rock failure mechanics with chemical damage is a new analysis method proposed by author. The method may explain and quantitatively analyze the mechanical effects of water and rock interaction.