The Asmari formation of A carbonate oilfield in Iraq is of mainly pore type, and the micro-fractures develop in part of the regions, which may lead to the change of permeability and relative permeability parameters, and thus result in the difference between the production and water cut of producers in micro-fracture developed region and those of producers in region without micro-fractures, influencing the development of oilfield. This paper uses the method of both oil and water phase index calculation via production dynamics data and reservoir numerical simulation to study the change of directional permeability(Kx/Ky) and relative permeability parameters when micro-fractures exist. The result shows that compared with the core experiment data without micro-fractures, the permeability increases along the micro-fracture extension direction (Kx/Ky increases), the four relative permeability parameters, namely oil phase index no, water phase index nw, residual oil saturation Sor and relative permeability of water phase under residual oil saturation Krw(Sor) all become smaller, which has been verified by the history match. This result has reference significance for the highly efficient simulation and accurately characterizing of micro-fractures in carbonate reservoirs.