3′-Daidzein sulfonate sodium is a new synthetic water-soluble compound derived from daidzein (an active ingredient of the kudzu vine root). It has been shown to have a protective effect on cerebral ischemia/reperfusion injury in rats. We plan to study the mechanism of its protective effect. 3′-Daidzein sulfonate sodium was injected in rats atfer cerebral ischemia/reperfusion injury. Results showed that 3′-daidzein sulfonate sodium signiifcantly reduced mitochondrial swelling, signiifcantly elevated the mitochondrial membrane potential, increased mi-tochondrial superoxide dismutase and glutathione peroxidase activities, and decreased mitochondrial malondialdehyde levels. 3′-Daidzein sulfonate sodium improved the structural integrity of the blood-brain barrier and reduced blood-brain barrier permeability. hTese ifndings conifrmed that 3′-daidzein sulfonate sodium has a protective effect on mitochondrial functions atfer cerebral ischemia/reperfusion injury, improves brain energy metabolism, and provides protection against blood-brain barrier damage.