When the ultrasonic wave disseminates in the air, there will be a speed difference between the downwind and the upwind. In the same sound path, the correlation method and phase difference measurement method are usually used to measure the wind speed. By comparing the advantages and disadvantages of the two methods, this paper proposes a new improved algorithm to measure the wind speed, which combines the correlation method and phase difference measurement method. At last we validate the algorithm superiority by simulation.