Abstract: The hydraulic fracture process is the fracture prolongation period when the formation is pressured by the fracture liquid.During the process, the flow character within the fracture greatly influenced on the fracture prolongation and shapes. To determine the fracture width in the hydraulic fracture process,
first, it will get the distributed law of the fluid pressure within the fracture, according to the hydraulics theory, and find the relationship between the fluid pressure and the fracture width. And then determine the fracture width or the direction of the coupled fluid-solid. Finally, calculate out the geometry parame-
ters of the fracture of the principle of rock mechanics and frac- ture mechanics. The paper derived out a new theoretical model described the flow field within the fracture by the study of the flow field within the fracture, and provided a theory for the so-lution of the 3-D fracture geometry parameters.

Key words: hydraulic fracture, fluid character, fracture width, fluid fields, coupled fluid and solid, Fracture geometry parametersn