Abstract: The optimum extracting technology of flavonoids in radix puerariae was investigated by using the factorial and orthogonal design. The results showed that 85 ℃, pH=8, 10∶1 of 70 % ethanol to radix puerariae weight ratio ,extract for 2 times and 3 hours for each time were optimal. The extraction rate was above 9 % and the flavonoid content of extract was above 40 %.