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There are various methods available to assist in the oil extraction from oil seeds, one of which is the use of ultrasonic waves. In this research, in order to optimize the process of extraction of oil from the peanut using ultrasound pretreatment, three levels of sonication time (0, 30 and 60 min) were used. After using these pretreatments, the oil of seeds was extracted with screw press with different rotation speeds (11, 34 and 57 rpm), then parameters including oil extraction yield, acidity, oxidative stability, peroxide, total phenolic compounds and refractive index of the samples were studied. Statistical analysis and process optimization was performed with the use of response surface methodology (RSM). The results showed that with increasing sonication time, oil extraction yield and phenolic compounds increased first and then decreased. By increasing the speed of the screw press, the amount of oil extraction yield and oxidative stability decreased, but the acidity, peroxide and total phenolic compounds increased. Increasing the sonication time also resulted in increased acidity, oxidative stability and peroxide reduction. On the other hand, it was determined that the parameters did not affect the rate of refractive index and its rate was 1.471 for all measured samples. According to the results of process optimization, it might be stated that with applying 60 minutes of ultrasound time and screw-rotation speed of the press of 21.73 rpm can provide a 0.766 utility for extracting oil from peanut. [ABSTRACT FROM AUTHOR]