The effect of Cr2O3 additive on nitridation of Si powder was studied at 1200 °C, 1300 °C and 1350 °C. At 1200 °C for 2 h, only Cr2N and CrSi2 peaks were found except Si in sample with 8 wt% Cr2O3. At 1300 °C, no visible Si3N4 peak was detected by XRD in pure Si sample, but in Cr2O3 added samples and with increasing of Cr2O3 additive the intensity of Si was reduced. At 1350 °C, Si peaks weakened in pure Si sample and Si powder was completely nitrided with Cr2O3 additive. The results showed that Cr2O3 additive improved the nitridation degree by the transformation between Cr2O3 and Cr2N and increasing the nitridation temperature promoted the nitridation of Si.