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The effect of calcium cyanamide (CaCN2) addition on the sintering of AlN ceramics was investigated. Pres sureless sintering was carried out with 0 to 3.0mass% CaCN2 addition, and densified sintered specimens (relative density>97.0%) were obtained using 1.0 to 2.0mass% CaCN2 addition depending on sintering tem perature and time. All of the sintered samples exclusively belong to the same AlN phase, and no other phases were found in the X-ray diffraction (XRD) patterns. A large fraction of intergranular fracture was found in the AlN samples sintered without and with CaCN2 additive in the scanning electron microscope (SEM) ob servations. The characterization of the ultrafine AlN powders sintered with CaCN2 additive was preformed with a microstructural analysis using a transmission electron microscope (TEM) attached with an energy dispersive X-ray analyzer (EDX) and electron diffraction (ED). Both microstructural results and sintering behavior in the AlN-CaCN2 system arise from the interaction between the Al2O3 surface covering the ultra fine AlN particles and the CaCN2 additive. Most oxygen impurity are removed from AlN as CO or CO2 gas and the residual oxygen impurity reacts to form the 3CaO•EAl2O3 phase, which is found at the grain boundaries.