Powder injection molding technique is an appropriate manufacturing process for 3-dimensional complex products. Nano powder was introduced in the process for microfabrication, but it increases the process difficulty and process cost. Nano/micro bimodal powder can be a solution to minimize the drawback of nano powder. Some research groups dealt with nano/micro bimodal powder injection molding process. However, most of their works only focused on the properties of sintered samples despite the importance of the injection molding step. Thus, in this study, the rheological property of nano/micro bimodal feedstocks was investigated with capillary rheometer. Flow index and flow activation energy were calculated from the result with the Arrhenius and powder law model. Moldability index was also obtained for each feedstock, and 12 % nano bimodal feedstock was regarded as the most desirable feedstock for injection molding process.