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In order to prepare dense B4C–SiC composites under relatively low temperature without any additive, stacking disordered B4C–SiC ultrafine composite powders were fabricated by mechanical alloying firstly. Subsequently, hot pressing sintering was applied to produce a dense B4C–SiC composite under relatively low temperature (1800–1950°C) without any additive. For the samples sintered at 1950°C for 30min, the obtained relative density, Vickers hardness, flexural strength and fracture toughness were 96%, 24GPa, 430MPa, and 4.6MPa.m1/2, respectively. The microstructural characterization showed that the main fracture mode was transgranular. The transgranular facture is caused by the powerful interfacial bonding between B4C and SiC. The density of the samples sintered with composite powders was 13% higher than the density of the samples sintered with mixed powders under the same conditions, indicating that the composite powders had an improved sintering activity due to their disordered structure. Meanwhile, the role of disorder–order transformation-driven sintering of ceramics was demonstrated. [ABSTRACT FROM AUTHOR]