The b–Si3N4 whisker randomly and unidirectionally reinforced Si3N4 composites were fabricated respectively. The high whisker alignment was obtained by extrusion processing. The R-curve behaviors were studied for the Si3N4 ceramics with addition of 3wt%, 5wt% and 10wt% b–Si3N4 whisker seeds respectively, and the effects of whisker orientation and content on the R-curve behaviors were analyzed and discussed. The ceramics with different whisker content and orientation showed well-defined R-curve behaviors. However, for the whisker random distribution, as its whisker content increased from 3wt% to 10wt%, the corresponding fracture toughness changed at an irregular trend; for the whisker unidirectional reinforcement, the fracture toughness in the direction perpendicular to whisker alignment was considerably improved, and most of indentation impressions tend to be very abnormal. The effects of whisker orientation and contents on the R-curve behaviors of the Si3N4 ceramics were further discussed.