A water and soil conservation and ecological restoration method of high and steep, abandoned slag piles at high elevation with large temperature differential in xerothermic drought valleys, comprises: preparing a mixed material; collecting and cutting a plant to obtain a plant ingredient; preparing a treated material; digging tree holes; planting; spreading the treated material, and watering. The water and soil conservation method adds gelling material for cover soil, and stirs to allow fine particles in the cover soil to be uniformly coated on the coarse particles to realize coherence, thus effectively avoiding water erosion and wind erosion on the loose cover soil on a slope and slag pile, reducing the cover soil falling into gaps of large slag pieces on the slope surface, thus controlling the water and cover soil conservation of a slag pile, and the scale of fill earth, and ensuring the survival rate and preservation rate of planted trees.