Using solubility parameter the solvent power of water-alcohol binary mixtures to extract the bio-ingredients from natural products was depicted. Practically, the extracted ingredients of polyphenols active to the radical scavenging and tyrosinase inhibition depended unpredictably on the solvent composition of water-alcohol mixtures. As such, in case of water-methanol the optimum extraction of polyphenols from Sophora japonica occurred at 60% of alcohol composition, at 80% in case of water-ethanol mixture, at 60% in case of water-n-propanol and at 40% in case of water-isopropanol . In addition, the bio-activities of the extractives such as radical scavenging and tyrosinase inhibitory effects were complicatedly varied with the water-alcohol mixtures and their compositions. However, when applying the solubility parameters indicating the polarity of the solvent mixtures, the solvent powers to extract the bio-ingredients at various water-alcohol mixtures and alcohol compositions could be simply expressed and the optimum solvent conditions for maximum extraction of the bio-ingredient could be easily predicted. It was also proven that such parameter was well applicable to bio-ingredient extractions from various natural products of Armeniacae Semen and Glycyrrhiza uralensis.