Ultrasound can be divided into three frequency ranges: power ultrasound, high frequency ultrasound and diagnostic ultrasound. Compared with high frequency ultrasound and ultrasonic diagnosis, power ultrasound generates larger cavitation bubbles resulting in higher temperatures and pressures in the cavitation zone. Power ultrasound has proven to be a very effective innovative technique of food processing, being applicable to many processes such as in the emulsification, crystallization, homogenization, cutting, hydrolysis and extraction of biologically active substances. However, some food products such as food natural pigments, antioxidants and some polysaccharides seem to present certain alterations after exposure to power ultrasound and these alterations may affect food quality and safety. At the same time, power ultrasound has also been applied to effective degradation of pesticide residues in food, increasing food quality and safety. In this paper, the principal mechanism and process parameters of ultrasound were summarized and the effects of power ultrasound on the degradation of food natural pigments, antioxidants, polysaccharides and pesticide residues in food processing were reviewed. The advantages and problems of applications of power ultrasound in food processing were analyzed to provide a comprehensive perspective for the applications of power ultrasound.