The nitrogen attack behavior of Fe-30.1Mn-5.7Al-2.9Cr-0.9C (in wt%) alloy was studied in the temperature ranged 950~1050℃ at 1 atm pure nitrogen atmosphere. Nitrogen attack caused by the inward diffusion of nitrogen is the typical style of nitriding. The nitriding kinetics followed parabolic rate law via the measurement of the depth of the internal attack. Because the nitrogen content in the middle region between the AlN needles was higher than the regions near AlN needles by the quasi-quantitative analysis of EDX in TEM, we could suggest that nitrogen diffused into the alloy matrix by volume diffusion and reacted with aluminum to form AlN.