Aiming at the impacts from climate warming and change of seasonal soil freeze-thaw pattern on the process of the soil nitrogen mineralization in alpine region, the soil nitrogen mineralization characteristics of the typical vegetation communities near the timberline of Wutai Mountain, such as meadow (CD), Larix principis-rupprechtii (HL), Picea meyeri(YS),etc.,are studied herein with the in-situ soil cultivation method. The result shows that the contents of NH_4~+ of all the communities are larger than those of NO_3~-. The total amount of the soil mineral nitrogen content (NH_4~+ + NO_3~-) of CD decreases in the onset of freezing period, increases in the deep freezing period, decreases in the thawing period and increases in the growing season. The total amounts of the soil mineral nitrogen contents of HL and YS decrease in the onset of freezing period and increase all along from the deep freezing period to the growing period. The net rates and amounts of the soil nitrogen mineralization of all the communities increase in the deep freezing period, decrease in the thawing period and increase in the growing period. No obvious differences are all along there between the total amounts of the soil mineral nitrogen and the net rates and amounts of the soil nitrogen mineralization of both HL and YS, while significant differences are there between CD and HL(p <0.05) and YS(p <0.05). The net rates and amounts of soil nitrogen mineralization of all the communities in the seasonal freeze-thaw period are lower than those in the growing period,but significant mineralizations exhibit as well. During the whole cultivation period (from freeze-thaw period to growing season),the nitrogen supply capability of HL is strongest, YS is the secondary and CD is the weakest. The freeze-thaw cycle can promote the soil nitrogen mineralization and increase the content of soil mineral nitrogen,thus provide the essential nutrients for the growth of plant in spring; however,this process also increases the risk of nutrients loss from soil. The study result provides a reference for the study on the soil nitrogen mineralization of ecosystem of alpine region.