The characteristics of the ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), and nitrogen mineralization rate were investigated using the method of in situ top-closed incubation in natural coniferous forests (Pinus sylvestris var. mongolica forest, Pinus sylvestris var. mongolica-Larix gmelinii mixed forest, and Larix gmelini forest) in Daxing'an Mountains. This study was aimed at comparing the characteristics of soil nitrogen mineralization in different forest types, and exploring the correlation between soil physical and chemical properties and nitrogen mineralization, which will help to improve soil nutrient and forest management in the Daxing'an Mountains. The results showed that the soil inorganic nitrogen in three forest types ranged from 31.51 to 70.42 mg/kg, of which > 90% was in the form of NH₄⁺-N during the observation period (5-10 months). The soil inorganic nitrogen content in the mixed forest was higher than that in the pure forest. The net nitrogen mineralization, ammonization, and nitrification rates of the three forest types were all negative in July and August and positive in other months with a clear seasonal pattern of a V-type change. The range of net nitrogen mineralization rate of the three forest types was -0.54 to 1.28 mg kg^-1 d^-1 (Pinus sylvestris var. mongolica forest), -0.13 to 0.55 mg kg^-1 d^-1 (Pinus sylvestris var. mongolica-Larix gmelinii mixed forest), and -0.80 to 1.05 mg kg^-1 d^-1 (Larix gmelini forest), respectively. The soil net ammonization dominated in the process of the soil nitrogen mineralization, and accounted for > 60% of the total amount of soil nitrogen mineralization. The vertical net nitrogen mineralization, net ammonization, and net nitrification rates were significantly different among the three forest types, with a significantly higher rate (P < 0.05) in the 0-10 cm soil layer than that in the 10-20 cm soil layer. Soil nitrogen mineralization rates were significantly correlated (P < 0.05) with soil moisture content, organic matter content, soil C/N, total nitrogen content, and C/N of the litter. We concluded that the characteristics of soil nitrogen mineralization were affected by the different quality of soils and litter in different forest types in the Daxing'an Mountains.