The invention relates to a working electrolyte of a 600-V aluminum electrolytic capacitor and the application of the working electrolyte. The working electrolyte comprises, by weight, 55-85% of a main solvent, 2-10% of a main solute, 1-7% of a subsidiary solute and 0.1-35% of an additive, wherein the main solvent is an alcohol solvent or an ester solvent or an ether solvent, and the main solute is high-grade fatty acid with the carbon number ranging from 20 to 40 and ammonium salt of the high-grade fatty acid. According to the working electrolyte, the proper high-grade fatty acid and the ammonium salt of the high-grade fatty acid are selected as the main solute, organic macromolecule polymer is selected as the additive resistant to a high temperature and a high voltage, and therefore the purpose that the aluminum electrolytic capacitor manufactured through the working electrolyte is resistant to a high voltage and a high temperature is achieved.