A relatively long time is required to determine the epoxide value of an epoxy resin or epoxy compound by chemical analysis (titration) methods, including the commonly used hydrochloric acid–acetone method, which may be referred to as the hydrochloric acid–acetone-standing method, because the mixture of epoxy resins or epoxy compounds, hydrochloric acid and acetone must be left standing in the dark for at least 30 min. In this study, ultrasonication was first introduced to this method, aiming to rapidly determine the epoxide value of an epoxy resin by accelerating the dissolution of epoxy resin in acetone solvent as well as the reaction between epoxide groups and hydrogen chloride. Further study of this approach was then carried out to determine the epoxide values of a series of epoxy resin–polyethylene glycol mixtures. This new approach which may be referred to as the hydrochloric acid–acetone-ultrasonication method provides a much faster and more accurate measurement of the epoxide value of an epoxy resin (within 2 min) or its mixture with polyethylene glycol (PEG-4000, within 5 min), compared to the hydrochloric acid–acetone-standing method. This ultrasonication method may be readily extended to other chemical analysis (titration) methods.