Abstract: The effect of ultrasound treated power and time on the structure and emulsibilities of bovine serum albumin( BSA)was studied by CD spectra,SDS- PAGE,ANS fluorescence probe emission spectra and UV absorption spectra. The results showed that ultrasound treatment had no significant influence on primary structure of BSA. However,it had a significant effect on secondary structure,tertiary structure. The content of α- helix were decreased. The content of β- sheet was increased. The content of β- turn firstly increased and then decreased with the increasing of ultrasound treatment,unordered had no significant change.Intrinsic fluorescence intensity,surface hydrophobicity and emulsibility were firstly increased and then decreased with the increasing of ultrasound treated power and time. The EAI and ESI of BSA reached the maximun when it was treated at240 W / cm2 for 10 min.It indicated that the ultrasound treatment would become a potential method for changing structure and emulsibilities of BSA.Meanwhile,when protein was emulsified by ultrasound treatment,it also provide a theoretical basis for the study of the mechanism of ultrasonic modification of protein.