The invention belongs to the field of soil fertilizer, and discloses a powder organic-inorganic water-soluble fertilizer and a preparing method thereof. The powder organic-inorganic water-soluble fertilizer comprises water-soluble organic matter, microelement water-soluble fertilizer, medium element water-soluble fertilizer, and a water-soluble anti-blocking agent. The content of nitrogen, phosphorous and potassium is larger than or equal to 30%, the content of calcium and magnesium is larger than 1%, and the content of organic matter is larger than 10%. According to the powder organic-inorganic water-soluble fertilizer and the preparing method thereof, the preparing technology is simple, the condition is mild, heating and fermenting are not needed, particles do not need to be prepared into, the four materials are directly uniformly mixed to prepare the powder organic-inorganic water-soluble fertilizer, the powder organic-inorganic water-soluble fertilizer can promote the absorption and utilization of crop to nitrogen, potassium, calcium and magnesium, soil beneficial microorganism reproduction is promoted, soil acidization and salinization are relieved, the crop root system growth is promoted, the utilization efficiency of crops to the water and nutrients is improved, the capability of the crops in resisting adversity is improved, and finally the purposes of increasing the yield and improving the product quality are achieved. Long term application of the powder organic-inorganic water-soluble fertilizer can also improve the soil structure and raise land fertility.