The optimization degree of the phase delays of the transducers directly affects the

precision degree of particle manipulation by the ultrasonic phased arrays. In this paper，an

improved adaptive genetic algorithm is proposed to optimize the phase delay of each transducer

in ultrasonic phased arrays. The algorithm not only has the characteristics of fast

convergence，stable convergence and good optimization effect，but also is insensitive to array size.

Four levitation points in the space are taken as examples to verify that the algorithm

has a good optimization effect on arbitrary levitation points in the space. The reliability of the algorithm is verified by

building acoustic levi- tation experiment of ultrasonic phased arrays to conduct levitation

experiments.