Abstract: The effects of ultrasound(20 kHz)at different levels of power output(200,400 and 600 W)on the solubility,emulsifying properties,foaming capacities,hydrolysis degree and surface hydrophobicity of royal jelly proteins(RJP)were investigated in this study. The secondary,tertiary structure and microstructure of were also analyzed to illustrate mechanism of ultrasound treatment on functional properties. The results showed that,compared with untreated royal jelly protein,the solubility of RJP increased by 10.90%,emulsifying activity index increased by 67.18%,emulsifying stability increased by 15.87%,foaming ability increased by 60.00%,foaming stability increased by 118.75%,hydrolysis degree increased by 83.33% and surface hydrophobicity increased by 18.65% after ultrasound treatment at 400 W. The secondary and tertiary structure analysis showed that ultrasound treatment at 400 W could induce unfolding of protein. The microstructure analysis showed that ultrasound treatment at 400 W could also result in cracked surface and small fragments. These results indicated that the improvement of functional properties was attributed to the changes in protein structure induced by ultrasound treatment.