The ecological environment of semi-arid mining area is fragile with the severe site conditions, so it is difficult for the ecological reconstruction and vegetation restoration. Medicago. Sativa, as an important restoration plant, not only has strong resistance to stress, but also is useful to improve soil structure and nutrients. Thus, restoration model of planting M. Sativa plays an important role in vegetation restoration in semi-arid mining areas. To assess the effects of planting time on soil improvement, the evolution of soil particles fractal characteristics were studied by using methods of field stratified sampling and indoor measuring. Planting fields of M. Sativa with 2, 4, 6 and 10 years(M2, M4, M6 and M10) were selected as the research objects, while the new dump without planting and that with natural restoration were chosen as control treatment. Based on the particle size of fractal theory, the soil particles fractal characteristics of different planting years and its relationship with soil properties were measured and analyzed. The results showed that the content of soil particle size in the study dump was mainly sand, followed by silt and least clay. Compared with the new dump without planting and that with natural restoration, the content of clay and silt particles as a whole showed a trend of first increasing and then decreasing as the recovery of planting M. Sativa processed, and reached the optimal level at M4 stage, while sand particles showed the opposite trend. The vertical profile of soil particle size varied in different models. The soil particle size of the new dump with natural restoration tended to be clay and silt particles on 0-10 cm soil, while that of M2 and M4 stage tended to clay and silt particles on 20-60 cm soil. The fractal dimension of soil varied from 2.09 to 2.57, first increasing and then decreasing during the recovery process of planting M. Sativa, and reaching the maximum at M4 stage. The fractal dimension of soil had extreme significantly positive correlation with clay and silt (P<0.01), and extreme significantly negative correlation with sand (P<0.01). The fractal dimension of soil was extreme significantly negative correlated with conductivity (P<0.01), significantly negative correlated with pH value and rapidly available potassium content (P<0.05), and significantly correlated positive with available nitrogen content (P<0.05). The soil fractal dimension can be used to determine the soil characteristics in the semi-arid mining dump. To sum up, the soil and vegetation population of planting M. Sativas will degrade after some restoration time, so it is necessary to pay attention to regulation of restoration time of planting M. Sativas. It is suggested that appropriate utilization and transformation should be carried out timely to ensure the sustainability of ecological restoration of mining abandon land in semi-arid region.