The spark plasma sintering behaviors of ZrB2-based ultra-high temperature ceramics were systematically investigated using nanosized ZrB2 powders. Rapid densification occurred at low temperature (1550 oC) for monolithic ZrB2 due to the nanosized powders. ZrB2-SiC ceramic achieved full densification at 1800 oC by SPS resulting in a high flexural strength of 1078±162 MPa. ZrB2-SiC-Cf composite was successfully prepared by SPS at 1700 oC. The composite showed obvious fiber pull-out on the fracture surface, leading to a high fracture toughness (6.04 MPa·m1/2) and a non-brittle fracture mode. Meanwhile, a high critical thermal shock temperature difference of 627 oC was obtained for ZrB2-SiC-Cf implying an excellent thermal shock resistance of such material.