The invention discloses a soil conditioner for avoiding soil hardening and reducing salt damage and a preparing method thereof. The soil conditioner is prepared from grass peat, biogas residues, meatbone meal, calcium humate, phosphomolybdic acid, thiourea, monopotassium phosphate, magnesium peroxide, a microbial agent, sodium alginate and raw traditional Chinese medicine materials, wherein the raw traditional Chinese medicine materials comprise fructus meliae azedarach, herba belladonnae, folium perillae, rhizoma acori graminei, rhizoma sinomeni cauliset, radix morindae officinalis and rhizoma cynanchi stauntonii. The preparing method comprises the steps of material selection, impurity removal, grinding, drying, uniform mixing and the like. According to the soil conditioner, the composition of the conditioner is considered from the aspect of nutrient balance, and the number of silfate ions causing soil hardening in the conditioner is also reduced; meanwhile, calcium humate promotingthe formation of soil granule structures is added, after application, soil is looser and more porous, the occurrence of soil hardening is reduced, the production cost is reduced, the growth of root systems of crops is promoted, yield increasing is obvious, the soil conditioner has the effect of preventing soil hardening, and the improvement of the soil structure is promoted.