The invention belongs to the technical field of fertilizers, and in particular relates to a 
lignin slow-release water-soluble 
fertilizer and a preparation method thereof. The 
lignin slow-release water-soluble 
fertilizer is prepared by adding a strong activating agent into an organic 
straw liquid, 
lignin, lignin-degrading 
enzyme; when the lignin is 
solid lignin, the weight parts of the organic 
straw liquid, the 
solid lignin and the lignin-degrading 
enzyme are 60-90 parts of the organic 
straw liquid, 10-40 parts of the 
solid lignin and 1-3 parts of the lignin-degrading 
enzyme; when the lignin is liquid lignin, the weight parts are 10-30 parts of the organic straw liquid, 70-100 parts of the liquid lignin and 1-3 parts of the lignin-degrading enzyme. The lignin slow-release water-soluble 
fertilizer provided by the invention has a slow-release function and water-soluble fertilizer properties as well, environmental 
pollution caused by comprehensive utilization of 
biomass raw materials is reduced, problems that a conventional slow-release water-soluble fertilizer is high in production cost, incomplete in 
nutrient component, relatively poor in 
fertility and the like can be solved, and modern organic planting of integral water and fertilizers can be achieved.