Ceramic bond cBN composites with large pores were prepared by firing at 740 ℃ for 1 h using Na2O-Al2O3-B2O3-SiO2 glass and cBN abrasives (particles size 0.150 mm/0.124 mm) as main starting materials, cBN micro-particles (particles size 0.014 mm) as the additive, and NH4HCO3 as the pore forming agent. The effect of NH4HCO3 and cBN micro-particles on the microstructure and properties of cBN composites was studied. The results show that for the cBN composite without cBN micro-particles the porosity obviously increases when the NH4HCO3 addition increases from 0 to 21 mass%, and increases slightly when the NH4HCO3 addition increases from 28 mass% to 42 mass%; and the bending strength decreases with the NH4HCO3 addition increasing. For the cBN composite with 14 mass% cBN micro-particles, the porosity increases continuously with the NH4HCO3 addition increasing, achieving 56.14% for the NH4HCO3 addition of 42 mass%, while, an obvious decrease of the bending strength is obtained. It is clearly indicated that the cBN micro-particles contribute to the high porosity and high strength of the porous ceramic bond cBN composites.