The effects of silane coupling agents on the injection molding process were investigated using silicone nitride mixtrues with a binder system containing polypropylene as a major binder (55vol% solid loading). The formation of bonding between silicon nitride powder and coupling agents was confirmed through the analyses of powder surface. The use of coupling agents improved mixing characteristics judged by the torque change during mixing process. the coupling agents also reduced molten viscosity of the mixture considerably, which is a main factor to determine the flow of the mixture. However, the bonding between coupling agents and polymers had a negative effect on the debinding process by retarding the thermal decomposition.