Production method of K acid

A production method of a K acid comprises the following steps: 1, mixing 2-naphthol (I) with 92-98% sulfuric acid, introducing a gas, and carrying out a primary sulfonation reaction to obtain a compound (II); 2, reacting the compound (II) with a potassium salt and an ammonium salt, and carrying out an ammonification reaction and sulfuric acid acidifying to obtain a compound (III); and 3, mixing the compound (III) with 95-98% sulfuric acid, introducing a gas, and carrying out a secondary sulfonation reaction to obtain a compound (IV) that is the K acid. The chemical equation of the method is shown in the description. The method effectively increases the utilization rate of sulfuric acid in the sulfonation process, greatly reduces the production amount of waste sulfuric acid and even industrial sulfates, avoids production operating inconvenience brought by use of 20% nicotinic acid and 65% nicotinic acid, improves the operability of the process, and also has the advantages of small sulfuric acid use amount, low production cost, high product quality and small environmental pollution.