Abstract: Geometry roughness of rock fractures affects the non-linear behavior of fluid flow through it. Com-bining with the series-parallel plate discrete model for rough fractures and COMSOL software,this paper analyzed the fluid flow ve- locity and pressure distribution in discrete model unit,and the physical mechanism of non-linear fluid flow occurred in fractures was obtained. By studying the law of geometry characteristic parameter effect on non-linear flow,a mass flow calculation method was proposed,and was compared with numerical results. It shows that the excess pressure loss taken place at aperture mutation position led to non-linear flow in rough fractures;it is the roughness of fracture wall coupled with Reynolds number which significantly influenced the non-linear flow behavior in rock fractures,and the max value of excess pressure loss arose in place which aperture obviously narrow;the proposed calculation method improved the analysis accuracy of results,displayed a better applicability.