Abstract: In this study, the compound 1-(4-(tert-butyl) phenyl)-3-hydroxy-2-methylpyridine-4 (1H) -one (hereinafter referred to as HAINU-19) was used as the active ingredient to prepare the microemulsion and determine its antifungal activity. First, through the screening solvents, co-solvents, and transparent, the formulation of 2.5% HAINU-19 microemulsion (mass fraction) was determined as follows: 2.5% HAINU-19, 15% ethanol, 10% cyclohexanone, 20% transparent (1601^# : 500^# : AC-1810 = 3 : 3 : 1), with distilled water making up to 100%. All indicators meet national standards. The bioassay result of pot experiments showed that the protective and curative effects of 2.5% HAINU-19 microemulsion on wheat stripe rust were 100% at 1000, 500, and 250-fold dilutions, and curative effects were 76.67%, 81.00%, and 82.33%, respectively. The field trial results showed that the 2.5% HAINU-19 microemulsion had a control efficacy of 86.13% on rice sheath blight at a 100-fold dilution and 71.24% at a 200-fold dilution. This study can provide an experimental basis and technical support for the development and application of the antifungal compound HAINU-19.