The invention provides a preparation process of 5,6-dimethyl-2-hydroxynicotinic acid 1. The preparation process of 5,6-dimethyl-2-hydroxynicotinic acid comprises the following steps: 1) performing a reaction on 2-butanone and ethyl formate in a proper solvent, under the existence of alkali and at proper temperature to obtain a compound 2; 2) performing condensation on the compound 2 and cyanoacetamide in a proper solvent and at proper temperature to obtain a compound 3; and 3) performing cyan-hydrolysis on the compound 3 under the existence of diluted acid to obtain 5,6-dimethyl-2-hydroxynicotinic acid 1. The synthesis route is as shown in the description. In the preparation process, the raw materials, the reagents and the solvents are the conventional synthesis reagents, and are cheap andeasily available; and the reaction condition of each step is mild, the aftertreatment operation is simple, the reaction yield is high and the product purity is high. The whole preparation cost of theproducts is low and the industrial production requirement is met.