The fractal properties of the spatial distribution pattern of different populations in Yunwushan Nature Reserve were reflected through the box dimensions. The result shows that Stipa bungeana Trin., Artemisia sacrorum Ledeb., and Thymus mongolicus Ronn. are dominant species of this area. The box dimensions of these species are around 1.7, and these dominant species occupied large ecological space in the area. But they didn′t get their highest box dimensions at the same time, Stipa bungeana Trin. and Thymus mongolicus Ronn. get their highest dimensions after enclosed for 20 years, and Artemisia sacrorum Ledeb. get the highest dimension in the 25th year of enclosure.