In the palm oil industry, the deacidification process is performed by steam stripping which causes the loss of most of palm oil's natural antioxidants due to high temperature. The liquid-liquid extraction process which is carried out at low temperature is preferable in order to preserve these compounds. The use of hydrated ethanol can reduce the losses of antioxidants, but the ability of this solvent to extract free fatty acids also decreases. Betaine monohydrate-based natural deep eutectic solvents (NADES) have extensive potential for this process. The selectivity of these NADES was determined to select a preferable solvent. The betaine monohydrate-glycerol NADES in a molar ratio of 1:8 was determined to be the preferred solvent with the highest selectivity. This solvent has an efficiency of palmitic acid extraction of 34.14%, and the amount of antioxidants can be preserved in the refined palm oil up to 99%. The compounds are stable during extraction.