Abstract: Nitriding reaction of Mn pellets prepared under different conditions was investigated with a self-made air-proofed nitriding system. The effects of Mn particle size, pelletizing pressure and binder content on the nitriding reaction were studied, and the real-time variation curves of temperature and Mn pellet mass were measured. The results show that with the decrease of particle size from 16-40 mesh to 60-80 mesh, the time for the pellet center temperature reaching peak (t_p) shifts from 164s to 101 s, the maximum temperature increment at the pellet center (ΔT_max) increases from 147 ℃ to 233 ℃, and the conversion ratio at 1 h rises from 90, 81% to 93.64%. With increasing pelletizing pressure from 266 MPa to 443 MPa, t_p decreases by 89 s, ΔT_max increases by 22 ℃, and the conversion ratio at 1 h rises from 91.59% to 94.92%. With the increase of binder addition from 1 g to 3 g, the conversion ratio at 1 h drops from 92.90% to 89.80%. The data points of the conversion rate and the nitriding time can be approximately fitted with the probability density function of the log-normal distribution.