In this study, we have established a green and efficient preparation method of quercetin. Rutin was first extracted from Sophora japonica using natural deep eutectic solvents (NADESs), then hydrolyzed into quercetin by rutin degrading enzyme (RDE) obtained from germinated tartary buckwheat in situ. Rutin solubility tests showed that most of the 11 NADESs increased the solubility of rutin by 67-3116 times compared to water. Thus, NADESs could be prior candidate to extract rutin. Extraction efficiency of rutin varied with different NADESs, and a maximum of 291.57 mg g(-1) was achieved in NADES ChGly, which was prepared by mixing choline chloride and glycerol at a molar ratio of 1:1. After that hydrolysis was performed directly in extraction system by adding RDE with degradation rate of up to 8.36 mg min(-1).L-1. Our findings suggest that preparation of quercetin using NADESs was simple and feasible to operate, environmentally friendly, efficient, and inspired the preparation method of bioactive components from a new perspective.