A carbide boronizing method was first developed to produce dense boron carbide- zirconium diboride (B4CZrB2) composites from zirconium carbide (ZrC) and amorphous boron powders (B) by Spark Plasma Sintering at 1800 degrees C2000 degrees C. The stoichiometry of B4C could be tailored by changing initial boron content, which also has an influence on the processing. The self-propagating high-temperature synthesis could be ignited by 1mol ZrC and 6mol B at around 1240 degrees C, whereas it was suppressed at a level of 10mol B. B8CZrB2 ceramics sintered at 1800 degrees C with 1mole ZrC and 10 mole B exhibited super high hardness (40.36GPa at 2.94N and 33.4GPa at 9.8N). The primary reason for the unusual high hardness of B8CZrB2 ceramics was considered to be the formation of nano-sized ZrB2 grains.