The present invention relates to a pyridone heterocyclic azo disperse dye and a preparation method thereof. The pyridone heterocyclic azo disperse dye is composed of two parts: namely a diazo component and a coupling component. The coupling component is composed of a heterocyclic active methylene compound or a heterocyclic phenolic compound that is coupled under the basic condition. The diazo component is composed of a weakly basic heterocyclic aromatic amine or a weakly basic aniline derivative. The preparation method comprises the steps of in the presence of a stabilizing agent, subjecting the weakly basic heterocyclic aromatic amine or the weakly basic aniline derivative to diazotization treatment in an organic solvent to precipitate a stable diazonium salt solid, filtering to obtain the solid, and applying the solid to alkaline coupling to obtain a target dye. The dye can be applied to the dyeing process of polyester fibers, polyamide fibers, polylactic acid fibers, polypropylene fibers and cellulose acetate fibers, and is excellent in dyeing brightness.