The invention discloses a water-soluble mineral fertilizer, belongs to the field of crop fertilizers, and particularly relates to a water-soluble inorganic mineral fertilizer. The water-soluble mineral fertilizer is composed of an A component, a B component and a C component, wherein the A component is composed of potash feldspar, powdered rock phosphate, medical stones, kieselguhr, bentonite and a water-soluble hydrophilic grafting agent; the B component is composed of urea, biological nitrogen-fixing bacteria, a urease inhibitor, a nitrification inhibitor and carboxymethyl starch, and the C component is composed of polyaspartic acid, polyyvinylpyrrolidone and casein. A preparation method of the water-soluble mineral fertilizer takes an inorganic mineral powder body as a main raw material, the water-soluble hydrophilic grafting agent is utilized, and the inorganic mineral powder body is dissolved in the water to form a stability colloid. The water-soluble mineral fertilizer provided by the invention contains a large number of nitrogen phosphorus and potassium elements and also contains different medium/trace elements and rare earth elements required by the growth of a plant, a soil structure is improved, the growth of the plant is improved, the product quality of a crop is improved, a raw material is easily available, the price is low, the raw material is non-pollution, the production technology is simple, and a market prospect is wide.