Soils of the 5 year sea-buckthorn and mountain peach mixed forest and the mountain peach pure forest in the semiarid degenerated mountain area were analyzed.Soil organic matter and nitrogen of the mountain peach and sea-buckthorn mixed forest were distinctly increased. In the 40-60 cm active layer of the forest root system,soil organic matter and nitrogen were higher than those of the mountain peach pure forest,and the increase in available phosphorus was less,and available potassium increased a little.