Crystallization of honey is a common process of the honey industry. Liquid honey is preferred by most of the consumers and by food companies for ease of handling and a better method compared to expensive and time-consuming heating is required to retard the crystallization process in honey, such as ultrasound. The present work details the treatment process for liquefying crystallized honey using highpower low -frequency ultrasound waves. This research is important to the concern within the honey industry that the heating used to liquefy crystallized honey is reducing the quality of honey, particularly its flavour. Therefore, it was necessary to determine whether it is feasible to replace the present heat treatment used for the liquefaction of naturally crystallized or candied honey with an ultrasound (US) treatment. The experiments were performed in an ultrasound bath and a thermal bath to compare the effectiveness of the treatments. First, the effect of an US treatment relative to heat treatment on the liquefaction of candied honey was studied via the viscosity and the crystal content. Second, the effect of the ultrasound treatment on honey quality was determined by analyzing the main quality parameters such as the hidroxymethylfurfural (HMF) content, the diastase and glucose-oxidase activity, the sugar composition and the water activity. The results obtained in this research point to a successful application of the ultrasound technology for the liquefaction of honey. Ultrasound treatment speeds up the liquefaction of honey in a temperature range of 40-50 ○C. Moreover, no increase of the HMF content was found and neither a decrease of the diastase activity. In addition, the ultrasound treatment did not affect the honey water activity, or the sugar composition. The crystal content of the ultrasound-treated samples presented a clearer and transparent honey than only heat-treated honey samples. The number and size of the crystals were also smallest. The only negative impact that was found is the diminution of the glucose oxidase activity after long periods of sonication for more than one hour.