Abstract: The second heat shock factor model of BNNTs reinforced ceramic composites was constructed based on Kingery thermal shock theory. The BNNTs/Si₃N₄ composites with weight fractions of 0.5wt%, 1.0wt%, 1.5wt% and 2.0wt% were prepared by hot pressed sintering process. The thermal shock resistance of the composite materials was tested by indentation method, verifying the second heat shock factor model in the steady state. The results indicate that the thermal shock performance of the material is enhanced by the BNNTs, with the increase of the second heat shock factor. Because the BNNTs which are distributed on the grain boundary make the crack pinned, bridged, and deflected, the crack propagation resistance is increased.