The invention discloses a humic acid-containing water-soluble fertilizer with a soil loosening function and a preparation method thereof. The preparation method comprises the step of dissolving and chelating the following raw materials in a reactor: high-quality polyacrylamide crystal which is an agricultural soil loosening agent, water-soluble humic acid, urea, monoammonium phosphate and potassium nitrate to produce the water soluble fertilizer which can be used for breaking through soil hardness, loosening soil, improving air permeability of soil, promoting microorganism activity of soil and enhancing fertilizer seepage force of soil and contains major elements, medium trace elements, humic acid and amino acid. The water-soluble fertilizer combines organic and inorganic matters, combines major elements and trace elements, and has the advantages of balancing nutrition, improving soil, improving the utilization ratio of nutrients and improving the yield and quality of crops.