Dense silicon nitride ceramics were prepared innovatively based on the fused deposition modeling (FDM) method with granular feedstock via screw extrusion. The printability of the feedstock, debinding process and typical printing defects were studied. The results show that the feedstock possesses an excellent printing performance and fits for printing unsupported small inclination angles, thin walls and complex curved surfaces. The organic binder system developed in this study combined with a two-step, “solving + heating” dedinding process has outstanding advantages in the preparation of thick-section parts and can achieve safe degreasing of green bodies with a thickness of 9 mm. It was revealed that the typical process defects of FDM include interlayer cracks and interpath pores. Combined with gas pressure sintering, dense silicon nitride ceramics with a bending strength of (774.5±70) MPa and a density of 3.25 g/cm³ were prepared, and silicon nitride ceramic parts with complex shapes and good shape keeping were successfully prepared.