NOVELTY - A humic acid containing controlled release potassium fertilizer in coated manner, comprises granular inorganic potassium salt, humic acid and bentonite, where ratio of granular potassium salt to humic acid to bentonite, in parts by weight, is 60-70:20-25:10-15. The inorganic potassium salt is potassium sulfate or potassium chloride.    USE - As humic acid containing controlled release potassium fertilizer (claimed).    ADVANTAGE - The controlled release potassium fertilizer rich in organic substances has high organic substance content, effectively controls the release of potassium fertilizer so as to reduce application of the potassium fertilizer, and reduces plant cost. The crops applied with the humic acid containing potassium fertilizer not only exhibits improved yield but also exhibits improved quality. The components improves utilization rate of fertilizer by more than 80%.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of controlled release potassium fertilizer involving: crushing: crushing humic acid and bentonite to grain size of 60-80 meshes; blending: fully stirring the humic acid and the bentonite according to weight ratio; preparing binder: uniformly mixing carboxymethyl cellulose, lignin with vegetable oil according to parts by weight of 1:1:1 to obtain binder; coating granules: sending the granular potassium salt to a disc granulator with rotated liquid spraying head, uniformly spraying the binder on the surface of the granular potassium salt, adding the blend of the humic acid and bentonite powder, repeating the process for 2 to 3 times till the grain size of the material in the disc is 2.5-3.5 mm, and the outer layer is black humic acid coating layer; drying: sending the coated granule to a drying system by a delivery device, raising temperature to 140 degrees C from 100 degrees C with hot air in half an hour and obtaining slow released granular controlled release potassium fertilizer having water content of less than or equal to 5% and containing organic substance.