Powder injection molding is one of the important manufacturing technologies for mass production of net-shape metallic and ceramic components. This technology combines the conventional plastic injection molding and the powder metallurgy consisting of four basic processes such as i)feedstock preparation, ii)injection molding, iii)debinding, and iv)sintering. Complex shaped magnetic components can be also efficiently made by this technology. To enhance the magnetic property of components, external magnetic field is applied to mold cavity during injection molding, which induces the alignment of anisotropic magnetic powders maximizing the total magnetic flux density. The interaction between magnetic field and feedstock lead to the change of rheological behavior, which makes it hard to find the proper injection molding condition. In this study, we have developed a magneto-rheological model taking the effect of various conditions during injection molding process, such as melt temperature, shear rate, powder volume fraction, particle size distribution, and external magnetic field. Our model represented well rheological behavior of feedstock and it can be very useful to optimize the injection molding process for magnetic components.