Functionalities, conformational characteristics and antioxidative capacities of sunflower meal protein isolate (SMPI) and its hydrolysates (SMPIH) at various degree of hydrolysis (DH) (6, 12, 18, 24%) were investigated following sonication. Enzymolysis notably enhanced the solubility, foaming properties and emulsion stability index (ESI) of untreated and sonicated SMPI at most examined pH. Nonetheless, emulsion activity index (EAI) of SMPI were more than SMPIH at all pH values, especially at pH 4.0–10.0 (P < 0.05). Compared with control, sonication improved solubility, foaming capacity and emulsification properties, but decreased foaming stability and had significant influence on the SMPI and SMPIH structure. Furthermore, sonication efficaciously enhanced reducing power and superoxide, and ABTS radical scavenging capacity of all preparations (P < 0.05) over control, confirmed by the analyses of hydrophobicities and content of amino acid compositions. Finally, our investigation suggests that sonicated SMPIH can create new opportunities for developing natural additives for different cosmetic, food and pharmacological preparations.