[Objective] The effect of seasonal freeze-thaw on soil micro-aggregates in the context of climate change was studied in order to provide references for the reserch of soil biochemical processes near the timberline.[Methods] Soil samples from three typical vegetation types (meadow, Larix principis-rupprechtii and Picea meyeri) near the timberline of Wutai Mountain were collected for soil column in situ experiment. Soil micro-aggregates contents and fractal dimensions (D) were measured.[Results] The variations of 2~0.25 mm and 0.25~0.05 mm aggregate contents were different among the three plots. The content of 0.05~0.02 mm aggregate reduced initially, then increased and finally reduced. The content of 0.02~0.002 mm aggregate reduced initially and then increased (except in Larix principis-rupprechtii plot), and the content of <0.002 mm micro-aggregates increased firstly and then reduced. The content of micro-aggregates changed significantly (p<0.05) due to seasonal freeze-thaw events in initial freezing and thawing periods, while there was no significant change in deep freezing period (p>0.05). Soil micro-aggregate contents also changed significantly (p<0.05) in the growing season. Different vegetation compositions caused significant differences (p<0.05) among micro-aggregate contents in three plots, especially, in initial freezing and thawing periods. During the freezing-thawing period, D values were increased, and that of Picea meyeri plots was the lowest. In growing season, D values were decreased, and that of meadou plots was the lowest. Significant differences (p<0.05) of D values among three researched plots were only observed in the late growing season, and the least D value is obtained in H. principis-rupprechtii.[Conclusion] Freeze-thaw cycles have great impacts on soil micro-aggregate contents. The responses of soil structures to seasonal freeze-thaw events are significantly different, and mainly occur in initial freezing period and thawing period. The D values of all plots are increased by freeze-thaw cycles. Although the D value of soil microaggregates increased during the incubation period, it gradually decreased to the pre-incubation level after entering the growing season. Soil aggregations and structures of all three plots vary periodically and have certain self-recovery capabilities.