The extraction of flavonoids from clovers (Trifolium) was optimized to maximize flavonoid yield in this study. A central composite design of response surface methodology involving extracting time, liquid-solid ratio, extracting temperature, and ethanol concentration was used, and second-order model for flavonoid yield was employed to generate the response surfaces. The optimum condition for flavonoid yield was determined as follows: 24 min extracting time, 20 liquid-solid ratio, 80°C extracting temperature, and 72% ethanol concentration. Under the optimum condition, the flavonoid yield was 2.29%. Key words: Clover, extraction, response surface methodology (RSM), flavonoid.