Metal Injection Molding deals with the complex fluid which consists of thermoplastic polymer medium and dense metallic powder suspensions to improve flowability and formability. To understand its fundamental mechanical behavior, it is important to consider powder structures and mechanics precisely. For the analysis of this process, a new granular model is proposed, which is based on the Distinct Element Method. Each element in this method is constituted by combining a metal powder with a binder (polymer) shell surrounding it. Both elasticity and viscosity for powder particles and binders are only considered in this mixture model as the constitutive relations. Thermo-mechanical coupling method with mapping/remapping procedure is introduced into the present granular model to deal with the cooling process. Several numerical results have demonstrated the effectiveness and validity of our developed granular modeling to deal with the various phenomena appearing in MIM process.