Abstract: In order to optimize the formula of hexaconazole microemulsion, the storage stability of hexaconazole ME at low temperature was studied by altering the components and dosage of solvents, surfactants and salts in the basic formula. The results showed that the stable period of ME was prolonged when the polarity of solvent system decreased, and the period was shortened when the polarity increased. When the polarity of solvent system was suitable, the stable period of of ME at low temperature would prolong as the dosage of hexaconazole increased. The storage stability of hexaconazole ME at low temperature was also affected by the type and content of surfactants. Among the same type of surfactants, as the HLB value decreased, the storage stability at low temperature increased. Alcohol compounds had significant impact on the storage stability of hexaconazole ME at low temperature. When the number of carbon in the compounds was less than 5, the stable period was shortened; when the number was equal to or more than 5, the stable period became longer. Addition of inorganic salts damaged the storage stability of hexaconazole ME at low temperature.