In this study, a new methodology is proposed based on using two periods of ultrasonication for the dehydration and desalting of heavy crude oil. For this purpose, ultrasonic irradiations are used under specified conditions such as irradiation input power, irradiation time and gap time after irradiation within a batch standing-wave resonator reactor. A serious problem with the commonly used single stage operation is that the enlarged water drops containing soluble salts in oil need to be settled for at least 60 min. To reduce this time, we proposed "two-stage ultrasonic irradiation at the equal irradiation times". This methodology proved to be an efficient way with the least settling time required. The results showed that the ultrasonic irradiations with irradiation input powers of 75W for primary irradiation and 50W for secondary irradiation (75-50W) at the equal irradiation times of 45 s considerably decreased the settling time to 5(x2)min. Moreover, dehydration rate was more than 96% and also the final salt content was up to 2.56 PTB, which can meet the need of refineries. Micrographs obtained also confirmed efficiency of the methodology which caused the water drop size to increase by 40% after each step of the process. (C) 2014 Elsevier B.V. All rights reserved.