NOVELTY - Producing natural humic acid water soluble fertilizer, comprises (i) filtering paper-making reconstituted tobacco waste liquid by using a filter mesh of 20-60 meshes, and separating; (ii) concentrating liquid; (iii) adding alkali solution, adjusting pH; (iv) adding composite biological agent into reaction container, and maintaining the reaction temperature; (v) drying the concentrate at the reaction end at low temperature until the water content is 20 plus minus 2%, and then transferring into the granulator t obtain granules; and (vi) drying the granules, until the water content is less than 15%.    USE - The method is useful for producing natural humic acid water soluble fertilizer (claimed).    ADVANTAGE - The method is economical, and suitable for agricultural production; and reduces the environmental pollution.    DETAILED DESCRIPTION - Producing natural humic acid water soluble fertilizer, comprises (i) filtering paper-making reconstituted tobacco waste liquid by using a filter mesh of 20-60 meshes, and separating, where the paper-making reconstituted tobacco waste liquid production is carried out in an extraction section, evaporation-concentration section, a coating section, and at least one section of waste liquid to produce a mixed waste liquid; (ii) adding the concentrated liquid phase into a concentrating device, and concentrating at low temperature under vacuum conditions, where the solid content in the concentrate is 20-50%; (iii) adding 10-20 wt.% alkali solution into the concentrate, adjusting the pH to 6.5 plus minus 0.3 by adding a mixture of 50% potassium hydroxide solution and 50% potassium dihydrogen phosphate solution into the alkali solution; (iv) feeding the concentrate into a reaction container under constant-temperature, adding 0.3-0.7 wt.% composite biological agent into the reaction container, and maintaining the reaction temperature at 33-38 degrees C, where the reaction time is 5-20 days, and the composite biological agent is commercially available composite yeast agent or a decomposing agent; (v) drying the concentrate at the reaction end at low temperature until the water content is 20 plus minus 2%, and then transferring into the granulator t obtain granules; and (vi) drying the granules having particle diameter of 1-4 mm, until the water content is less than 15%.