The invention discloses a biochemical humic acid-containing liquid nitrogenous fertilizer and a preparation method thereof. The biochemical humic acid-containing liquid nitrogenous fertilizer is prepared through a chemical reaction of 42-47mass% of ammonium nitrate and 30-37mass% of urea added to 16-28mass% of a solvent adopting a self-made biochemical humic acid concentrate liquid at a certain temperature. The biochemical humic acid-containing liquid nitrogenous fertilizer has the advantages of fertilizer efficiency improvement, fertilizer loss and environment pollution reduction, good energy saving and consumption reduction effects, good safety and low transportation cost, and also has the advantages of strong function group penetration, good water solubility, and easy absorption by plants due to containing of biochemical humic acid prepared through microbial fermentation of furfural residues and other crop stalks; and the product preparation method fully recycles the solid wastes furfural residues, and solves the environment problem caused by bulk deposition of solid wastes in the furfural industry.