According to the characteristics of hydraulic fracturing of rock mass and concrete fracture under natural power, the water infusion model and iteration procedure of rock or concrete fracture under constant water head were built based on the cube law of water moving in fracture. The different infusion processes were calculated by changing opening width, inner surface off set and shape of fracture. The results showed that the water moving in fracture is fast in initial infusion stage, and slow in final. The water pressure along the fracture is gradually developed to full pressure as lapse. When the opening width of fracture is larger than 0.02 mm, there is shorter time to arrive tip and the pressure along the fracture is a whole head. When the opening width of fracture is micrometer, it is difficulty to fill fracture, which is an impermeable fracture. The influence of fracture water pressure on relative smaller opening width fracture due to inner surface off-set is more significant than that with wider opening width of fracture.
