Incidence of defects in MoSi2 rods prepared by continuous extrusion is dependent on the viscosity of binder. Generally, low viscosity results in surface defects while high viscosity is responsible for inner defects. Cross-section observations indicated that the typical inner defects in sintered MoSi2 rods were large fissure cavity, multiple small holes and single small cavity, of which the characteristic ultrasonic reflection patterns have been experimentally established. Formation of the inner defects is attributed to the inhomogeneous feedstock moving behavior in die, which is aggravated with increasing viscosity of binder. Defect free MoSi2 rods were prepared successfully via continuous extrusion by carefully controlling the viscosity of binder.