For the damage process of rock is a kind of energy-consuming process in nature, it should conform to the least energy consumption principle. Here, a new damage evolution model based on the least energy consumption principle is proposed. With real experiments of granite specimens, the new model is verified. It can be seen that, the stress-strain curves (part before the peak) of the theoretical curve is coincided with the test curve well. So, this new method is suitable to describe the evolution process of rock damage.