The work aims to improve efficiency of electroless plating and coating performance. The effects of different ultrasonic conditions on electroless plating of Ni-P alloy coating were studied provided with ultrasonic power of 90~150 W and frequency of 20 kHz and 40 kHz by using common chemical plating bath formula. The influence of ultrasonic power and frequency on properties of the plating was analyzed by virtue of such characterization methods as deposition rate, porosity, HV, XRD, Scanning Electron Microscope and EDS. Quality of the ultrasonic-assisted electroless plating surface improved, the porosity decreased significantly and the deposition rate increased greatly. The deposition rate increased as the power and frequency increased. The deposition rate was 15 μm/h, the highest provided with the ultrasonic frequency of 40 kHz and power of 150 W, and 83% higher than that of water bath (8.2 μm/h). The hardness of the plating increased and could be up to 585HV as the ultrasonic power and frequency increased, 25% higher than that of water bath (468HV). In addition, ultrasonic could change P content of the plating and improve the crystallinity. The ultrasonic assisting can enhance electroless plating rate and improve the coating performance. Provided with the ultrasonic frequency of 40 kHz and power of 150 W, overall quality of the plating is the best, corrosion resistance is better and this process is most practical.