Abstract: Phased array high intensity focused ultrasound can control the shape, position and number of foci in a specific area. Additionally, it allows us to obtain high precision and high efficiency for therapeutic ultrasound. We will briefly review the principles of phased array focused ultrasound and some materials used for transducers. Specifically, we will discuss relevant array and circuit designs, methods for controlling the acoustic signals from multiple transducer elements, and techniques to optimize the acoustic field.