The invention provides a conditioner for artificial soil on a slope with the function of water retention, which is prepared by the following raw materials according to weight percentage by compounding and mixing: 10 to 25 percent of livestock manure, 25 to 50 percent of super absorbent resin, 5 to 15 percent of ground phosphorite, 1 to 5 percent of anhydrite powder, 20 to 35 percent of humic acid, 5 to 10 percent of zeolite powder, 1 to 10 percent of chitosan, 0 to 10 pecent of bentonite, 0 to 5 percent of phosphate ester and 0 to 5 percent of citrate acid. The conditioner has obvious effects of enhancing the water retention of soil, reducing the water loss and soil erosion, improving the physical and chemical properties of soil and promoting the revegetation.